diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index 52912ab971..04b2a61fe8 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -4460,106 +4460,6 @@ parameters:
 			count: 1
 			path: src/PhpSpreadsheet/Reader/Xlsx/SheetViewOptions.php
 
-		-
-			message: "#^Method PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:dxfs\\(\\) has no return type specified\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Method PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:dxfs\\(\\) has parameter \\$readDataOnly with no type specified\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Method PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:getArrayItem\\(\\) has no return type specified\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Method PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:getArrayItem\\(\\) has parameter \\$array with no type specified\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Method PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:getArrayItem\\(\\) has parameter \\$key with no type specified\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Method PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:readColor\\(\\) has no return type specified\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Method PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:readColor\\(\\) has parameter \\$background with no type specified\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Method PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:readColor\\(\\) has parameter \\$color with no type specified\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Method PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:readProtectionHidden\\(\\) has parameter \\$style with no type specified\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Method PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:readProtectionLocked\\(\\) has parameter \\$style with no type specified\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Method PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:readStyle\\(\\) has parameter \\$style with no type specified\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Method PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:setStyleBaseData\\(\\) has parameter \\$cellStyles with no type specified\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Method PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:setStyleBaseData\\(\\) has parameter \\$styles with no type specified\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Method PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:styles\\(\\) has no return type specified\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Parameter \\#1 \\$hexColourValue of static method PhpOffice\\\\PhpSpreadsheet\\\\Style\\\\Color\\:\\:changeBrightness\\(\\) expects string, string\\|null given\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Parameter \\#2 \\$alignmentXml of static method PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:readAlignmentStyle\\(\\) expects SimpleXMLElement, object given\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Property PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:\\$cellStyles has no type specified\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Property PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:\\$styleXml has no type specified\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Property PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:\\$styles has no type specified\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
-		-
-			message: "#^Static property PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Styles\\:\\:\\$theme \\(PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Theme\\) does not accept PhpOffice\\\\PhpSpreadsheet\\\\Reader\\\\Xlsx\\\\Theme\\|null\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xlsx/Styles.php
-
 		-
 			message: "#^Parameter \\#1 \\$haystack of function strpos expects string, string\\|false given\\.$#"
 			count: 1
diff --git a/src/PhpSpreadsheet/Reader/Xlsx.php b/src/PhpSpreadsheet/Reader/Xlsx.php
index c8b9126cbe..4417fe7d53 100644
--- a/src/PhpSpreadsheet/Reader/Xlsx.php
+++ b/src/PhpSpreadsheet/Reader/Xlsx.php
@@ -19,6 +19,7 @@
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx\SheetViewOptions;
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx\SheetViews;
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx\Styles;
+use PhpOffice\PhpSpreadsheet\Reader\Xlsx\Theme;
 use PhpOffice\PhpSpreadsheet\ReferenceHelper;
 use PhpOffice\PhpSpreadsheet\RichText\RichText;
 use PhpOffice\PhpSpreadsheet\Settings;
@@ -34,7 +35,6 @@
 use PhpOffice\PhpSpreadsheet\Worksheet\HeaderFooterDrawing;
 use PhpOffice\PhpSpreadsheet\Worksheet\Worksheet;
 use SimpleXMLElement;
-use stdClass;
 use Throwable;
 use XMLReader;
 use ZipArchive;
@@ -50,18 +50,14 @@ class Xlsx extends BaseReader
      */
     private $referenceHelper;
 
-    /**
-     * Xlsx\Theme instance.
-     *
-     * @var Xlsx\Theme
-     */
-    private static $theme;
-
     /**
      * @var ZipArchive
      */
     private $zip;
 
+    /** @var Styles */
+    private $styleReader;
+
     /**
      * Create a new Xlsx Reader instance.
      */
@@ -406,6 +402,8 @@ public function load(string $filename, int $flags = 0): Spreadsheet
         //    Read the theme first, because we need the colour scheme when reading the styles
         [$workbookBasename, $xmlNamespaceBase] = $this->getWorkbookBaseName();
         $wbRels = $this->loadZip("xl/_rels/${workbookBasename}.rels", Namespaces::RELATIONSHIPS);
+        $theme = null;
+        $this->styleReader = new Styles();
         foreach ($wbRels->Relationship as $relx) {
             $rel = self::getAttributes($relx);
             $relTarget = (string) $rel['Target'];
@@ -438,7 +436,8 @@ public function load(string $filename, int $flags = 0): Spreadsheet
                             $themeColours[$themePos] = (string) $xmlColourData['val'];
                         }
                     }
-                    self::$theme = new Xlsx\Theme($themeName, $colourSchemeName, $themeColours);
+                    $theme = new Theme($themeName, $colourSchemeName, $themeColours);
+                    $this->styleReader->setTheme($theme);
 
                     break;
             }
@@ -599,7 +598,7 @@ public function load(string $filename, int $flags = 0): Spreadsheet
 
                             // add style to cellXf collection
                             $objStyle = new Style();
-                            self::readStyle($objStyle, $style);
+                            $this->styleReader->readStyle($objStyle, $style);
                             if ($addingFirstCellXf) {
                                 $excel->removeCellXfByIndex(0); // remove the default style
                                 $addingFirstCellXf = false;
@@ -634,7 +633,7 @@ public function load(string $filename, int $flags = 0): Spreadsheet
 
                             // add style to cellStyleXf collection
                             $objStyle = new Style();
-                            self::readStyle($objStyle, $cellStyle);
+                            $this->styleReader->readStyle($objStyle, $cellStyle);
                             if ($addingFirstCellStyleXf) {
                                 $excel->removeCellStyleXfByIndex(0); // remove the default style
                                 $addingFirstCellStyleXf = false;
@@ -642,10 +641,10 @@ public function load(string $filename, int $flags = 0): Spreadsheet
                             $excel->addCellStyleXf($objStyle);
                         }
                     }
-                    $styleReader = new Styles($xmlStyles);
-                    $styleReader->setStyleBaseData(self::$theme, $styles, $cellStyles);
-                    $dxfs = $styleReader->dxfs($this->readDataOnly);
-                    $styles = $styleReader->styles();
+                    $this->styleReader->setStyleXml($xmlStyles);
+                    $this->styleReader->setStyleBaseData($theme, $styles, $cellStyles);
+                    $dxfs = $this->styleReader->dxfs($this->readDataOnly);
+                    $styles = $this->styleReader->styles();
 
                     $xmlWorkbook = $this->loadZipNoNamespace($relTarget, $mainNS);
                     $xmlWorkbookNS = $this->loadZip($relTarget, $mainNS);
@@ -718,7 +717,7 @@ public function load(string $filename, int $flags = 0): Spreadsheet
                                 }
 
                                 $sheetViewOptions = new SheetViewOptions($docSheet, $xmlSheet);
-                                $sheetViewOptions->load($this->getReadDataOnly());
+                                $sheetViewOptions->load($this->getReadDataOnly(), $this->styleReader);
 
                                 (new ColumnAndRowAttributes($docSheet, $xmlSheet))
                                     ->load($this->getReadFilter(), $this->getReadDataOnly());
@@ -1618,45 +1617,6 @@ public function load(string $filename, int $flags = 0): Spreadsheet
         return $excel;
     }
 
-    /**
-     * @param SimpleXMLElement|stdClass $style
-     */
-    private static function readStyle(Style $docStyle, $style): void
-    {
-        $docStyle->getNumberFormat()->setFormatCode($style->numFmt);
-
-        // font
-        if (isset($style->font)) {
-            Styles::readFontStyle($docStyle->getFont(), $style->font);
-        }
-
-        // fill
-        if (isset($style->fill)) {
-            Styles::readFillStyle($docStyle->getFill(), $style->fill);
-        }
-
-        // border
-        if (isset($style->border)) {
-            Styles::readBorderStyle($docStyle->getBorders(), $style->border);
-        }
-
-        // alignment
-        if (isset($style->alignment)) {
-            Styles::readAlignmentStyle($docStyle->getAlignment(), $style->alignment);
-        }
-
-        // protection
-        if (isset($style->protection)) {
-            Styles::readProtectionLocked($docStyle, $style);
-            Styles::readProtectionHidden($docStyle, $style);
-        }
-
-        // top-level style settings
-        if (isset($style->quotePrefix)) {
-            $docStyle->setQuotePrefix((bool) $style->quotePrefix);
-        }
-    }
-
     /**
      * @return RichText
      */
@@ -1685,7 +1645,7 @@ private function parseRichText(?SimpleXMLElement $is)
                             $objText->getFont()->setSize((float) $attr['val']);
                         }
                         if (isset($run->rPr->color)) {
-                            $objText->getFont()->setColor(new Color(Styles::readColor($run->rPr->color)));
+                            $objText->getFont()->setColor(new Color($this->styleReader->readColor($run->rPr->color)));
                         }
                         if (isset($run->rPr->b)) {
                             $attr = $run->rPr->b->attributes();
diff --git a/src/PhpSpreadsheet/Reader/Xlsx/SheetViewOptions.php b/src/PhpSpreadsheet/Reader/Xlsx/SheetViewOptions.php
index 123588182b..a302cc5692 100644
--- a/src/PhpSpreadsheet/Reader/Xlsx/SheetViewOptions.php
+++ b/src/PhpSpreadsheet/Reader/Xlsx/SheetViewOptions.php
@@ -17,17 +17,14 @@ public function __construct(Worksheet $workSheet, ?SimpleXMLElement $worksheetXm
         $this->worksheetXml = $worksheetXml;
     }
 
-    /**
-     * @param bool $readDataOnly
-     */
-    public function load($readDataOnly = false): void
+    public function load(bool $readDataOnly, Styles $styleReader): void
     {
         if ($this->worksheetXml === null) {
             return;
         }
 
         if (isset($this->worksheetXml->sheetPr)) {
-            $this->tabColor($this->worksheetXml->sheetPr);
+            $this->tabColor($this->worksheetXml->sheetPr, $styleReader);
             $this->codeName($this->worksheetXml->sheetPr);
             $this->outlines($this->worksheetXml->sheetPr);
             $this->pageSetup($this->worksheetXml->sheetPr);
@@ -42,10 +39,10 @@ public function load($readDataOnly = false): void
         }
     }
 
-    private function tabColor(SimpleXMLElement $sheetPr): void
+    private function tabColor(SimpleXMLElement $sheetPr, Styles $styleReader): void
     {
-        if (isset($sheetPr->tabColor, $sheetPr->tabColor['rgb'])) {
-            $this->worksheet->getTabColor()->setARGB((string) $sheetPr->tabColor['rgb']);
+        if (isset($sheetPr->tabColor)) {
+            $this->worksheet->getTabColor()->setARGB($styleReader->readColor($sheetPr->tabColor));
         }
     }
 
diff --git a/src/PhpSpreadsheet/Reader/Xlsx/Styles.php b/src/PhpSpreadsheet/Reader/Xlsx/Styles.php
index 72e66a9911..550c52c0e9 100644
--- a/src/PhpSpreadsheet/Reader/Xlsx/Styles.php
+++ b/src/PhpSpreadsheet/Reader/Xlsx/Styles.php
@@ -13,35 +13,44 @@
 use PhpOffice\PhpSpreadsheet\Style\Protection;
 use PhpOffice\PhpSpreadsheet\Style\Style;
 use SimpleXMLElement;
+use stdClass;
 
 class Styles extends BaseParserClass
 {
     /**
      * Theme instance.
      *
-     * @var Theme
+     * @var ?Theme
      */
-    private static $theme;
+    private $theme;
 
+    /** @var array */
     private $styles = [];
 
+    /** @var array */
     private $cellStyles = [];
 
+    /** @var SimpleXMLElement */
     private $styleXml;
 
-    public function __construct(SimpleXMLElement $styleXml)
+    public function setStyleXml(SimpleXmlElement $styleXml): void
     {
         $this->styleXml = $styleXml;
     }
 
-    public function setStyleBaseData(?Theme $theme = null, $styles = [], $cellStyles = []): void
+    public function setTheme(Theme $theme): void
     {
-        self::$theme = $theme;
+        $this->theme = $theme;
+    }
+
+    public function setStyleBaseData(?Theme $theme = null, array $styles = [], array $cellStyles = []): void
+    {
+        $this->theme = $theme;
         $this->styles = $styles;
         $this->cellStyles = $cellStyles;
     }
 
-    public static function readFontStyle(Font $fontStyle, SimpleXMLElement $fontStyleXml): void
+    public function readFontStyle(Font $fontStyle, SimpleXMLElement $fontStyleXml): void
     {
         if (isset($fontStyleXml->name, $fontStyleXml->name['val'])) {
             $fontStyle->setName((string) $fontStyleXml->name['val']);
@@ -60,7 +69,7 @@ public static function readFontStyle(Font $fontStyle, SimpleXMLElement $fontStyl
                 !isset($fontStyleXml->strike['val']) || self::boolean((string) $fontStyleXml->strike['val'])
             );
         }
-        $fontStyle->getColor()->setARGB(self::readColor($fontStyleXml->color));
+        $fontStyle->getColor()->setARGB($this->readColor($fontStyleXml->color));
 
         if (isset($fontStyleXml->u) && !isset($fontStyleXml->u['val'])) {
             $fontStyle->setUnderline(Font::UNDERLINE_SINGLE);
@@ -78,7 +87,7 @@ public static function readFontStyle(Font $fontStyle, SimpleXMLElement $fontStyl
         }
     }
 
-    private static function readNumberFormat(NumberFormat $numfmtStyle, SimpleXMLElement $numfmtStyleXml): void
+    private function readNumberFormat(NumberFormat $numfmtStyle, SimpleXMLElement $numfmtStyleXml): void
     {
         if ($numfmtStyleXml->count() === 0) {
             return;
@@ -89,7 +98,7 @@ private static function readNumberFormat(NumberFormat $numfmtStyle, SimpleXMLEle
         }
     }
 
-    public static function readFillStyle(Fill $fillStyle, SimpleXMLElement $fillStyleXml): void
+    public function readFillStyle(Fill $fillStyle, SimpleXMLElement $fillStyleXml): void
     {
         if ($fillStyleXml->gradientFill) {
             /** @var SimpleXMLElement $gradientFill */
@@ -99,16 +108,16 @@ public static function readFillStyle(Fill $fillStyle, SimpleXMLElement $fillStyl
             }
             $fillStyle->setRotation((float) ($gradientFill['degree']));
             $gradientFill->registerXPathNamespace('sml', Namespaces::MAIN);
-            $fillStyle->getStartColor()->setARGB(self::readColor(self::getArrayItem($gradientFill->xpath('sml:stop[@position=0]'))->color));
-            $fillStyle->getEndColor()->setARGB(self::readColor(self::getArrayItem($gradientFill->xpath('sml:stop[@position=1]'))->color));
+            $fillStyle->getStartColor()->setARGB($this->readColor(self::getArrayItem($gradientFill->xpath('sml:stop[@position=0]'))->color));
+            $fillStyle->getEndColor()->setARGB($this->readColor(self::getArrayItem($gradientFill->xpath('sml:stop[@position=1]'))->color));
         } elseif ($fillStyleXml->patternFill) {
             $defaultFillStyle = Fill::FILL_NONE;
             if ($fillStyleXml->patternFill->fgColor) {
-                $fillStyle->getStartColor()->setARGB(self::readColor($fillStyleXml->patternFill->fgColor, true));
+                $fillStyle->getStartColor()->setARGB($this->readColor($fillStyleXml->patternFill->fgColor, true));
                 $defaultFillStyle = Fill::FILL_SOLID;
             }
             if ($fillStyleXml->patternFill->bgColor) {
-                $fillStyle->getEndColor()->setARGB(self::readColor($fillStyleXml->patternFill->bgColor, true));
+                $fillStyle->getEndColor()->setARGB($this->readColor($fillStyleXml->patternFill->bgColor, true));
                 $defaultFillStyle = Fill::FILL_SOLID;
             }
 
@@ -120,7 +129,7 @@ public static function readFillStyle(Fill $fillStyle, SimpleXMLElement $fillStyl
         }
     }
 
-    public static function readBorderStyle(Borders $borderStyle, SimpleXMLElement $borderStyleXml): void
+    public function readBorderStyle(Borders $borderStyle, SimpleXMLElement $borderStyleXml): void
     {
         $diagonalUp = self::boolean((string) $borderStyleXml['diagonalUp']);
         $diagonalDown = self::boolean((string) $borderStyleXml['diagonalDown']);
@@ -134,24 +143,24 @@ public static function readBorderStyle(Borders $borderStyle, SimpleXMLElement $b
             $borderStyle->setDiagonalDirection(Borders::DIAGONAL_BOTH);
         }
 
-        self::readBorder($borderStyle->getLeft(), $borderStyleXml->left);
-        self::readBorder($borderStyle->getRight(), $borderStyleXml->right);
-        self::readBorder($borderStyle->getTop(), $borderStyleXml->top);
-        self::readBorder($borderStyle->getBottom(), $borderStyleXml->bottom);
-        self::readBorder($borderStyle->getDiagonal(), $borderStyleXml->diagonal);
+        $this->readBorder($borderStyle->getLeft(), $borderStyleXml->left);
+        $this->readBorder($borderStyle->getRight(), $borderStyleXml->right);
+        $this->readBorder($borderStyle->getTop(), $borderStyleXml->top);
+        $this->readBorder($borderStyle->getBottom(), $borderStyleXml->bottom);
+        $this->readBorder($borderStyle->getDiagonal(), $borderStyleXml->diagonal);
     }
 
-    private static function readBorder(Border $border, SimpleXMLElement $borderXml): void
+    private function readBorder(Border $border, SimpleXMLElement $borderXml): void
     {
         if (isset($borderXml['style'])) {
             $border->setBorderStyle((string) $borderXml['style']);
         }
         if (isset($borderXml->color)) {
-            $border->getColor()->setARGB(self::readColor($borderXml->color));
+            $border->getColor()->setARGB($this->readColor($borderXml->color));
         }
     }
 
-    public static function readAlignmentStyle(Alignment $alignment, SimpleXMLElement $alignmentXml): void
+    public function readAlignmentStyle(Alignment $alignment, SimpleXMLElement $alignmentXml): void
     {
         $alignment->setHorizontal((string) $alignmentXml['horizontal']);
         $alignment->setVertical((string) $alignmentXml['vertical']);
@@ -174,43 +183,53 @@ public static function readAlignmentStyle(Alignment $alignment, SimpleXMLElement
         );
     }
 
-    private function readStyle(Style $docStyle, $style): void
+    /**
+     * Read style.
+     *
+     * @param SimpleXMLElement|stdClass $style
+     */
+    public function readStyle(Style $docStyle, $style): void
     {
         if ($style->numFmt instanceof SimpleXMLElement) {
-            self::readNumberFormat($docStyle->getNumberFormat(), $style->numFmt);
+            $this->readNumberFormat($docStyle->getNumberFormat(), $style->numFmt);
         } else {
             $docStyle->getNumberFormat()->setFormatCode($style->numFmt);
         }
 
         if (isset($style->font)) {
-            self::readFontStyle($docStyle->getFont(), $style->font);
+            $this->readFontStyle($docStyle->getFont(), $style->font);
         }
 
         if (isset($style->fill)) {
-            self::readFillStyle($docStyle->getFill(), $style->fill);
+            $this->readFillStyle($docStyle->getFill(), $style->fill);
         }
 
         if (isset($style->border)) {
-            self::readBorderStyle($docStyle->getBorders(), $style->border);
+            $this->readBorderStyle($docStyle->getBorders(), $style->border);
         }
 
-        if (isset($style->alignment->alignment)) {
-            self::readAlignmentStyle($docStyle->getAlignment(), $style->alignment);
+        if (isset($style->alignment)) {
+            $this->readAlignmentStyle($docStyle->getAlignment(), $style->alignment);
         }
 
         // protection
         if (isset($style->protection)) {
-            self::readProtectionLocked($docStyle, $style);
-            self::readProtectionHidden($docStyle, $style);
+            $this->readProtectionLocked($docStyle, $style);
+            $this->readProtectionHidden($docStyle, $style);
         }
 
         // top-level style settings
         if (isset($style->quotePrefix)) {
-            $docStyle->setQuotePrefix(true);
+            $docStyle->setQuotePrefix((bool) $style->quotePrefix);
         }
     }
 
-    public static function readProtectionLocked(Style $docStyle, $style): void
+    /**
+     * Read protection locked attribute.
+     *
+     * @param SimpleXMLElement|stdClass $style
+     */
+    public function readProtectionLocked(Style $docStyle, $style): void
     {
         if (isset($style->protection['locked'])) {
             if (self::boolean((string) $style->protection['locked'])) {
@@ -221,7 +240,12 @@ public static function readProtectionLocked(Style $docStyle, $style): void
         }
     }
 
-    public static function readProtectionHidden(Style $docStyle, $style): void
+    /**
+     * Read protection hidden attribute.
+     *
+     * @param SimpleXMLElement|stdClass $style
+     */
+    public function readProtectionHidden(Style $docStyle, $style): void
     {
         if (isset($style->protection['hidden'])) {
             if (self::boolean((string) $style->protection['hidden'])) {
@@ -232,18 +256,18 @@ public static function readProtectionHidden(Style $docStyle, $style): void
         }
     }
 
-    public static function readColor($color, $background = false)
+    public function readColor(SimpleXMLElement $color, bool $background = false): string
     {
         if (isset($color['rgb'])) {
             return (string) $color['rgb'];
         } elseif (isset($color['indexed'])) {
-            return Color::indexedColor($color['indexed'] - 7, $background)->getARGB();
+            return Color::indexedColor((int) ($color['indexed'] - 7), $background)->getARGB() ?? '';
         } elseif (isset($color['theme'])) {
-            if (self::$theme !== null) {
-                $returnColour = self::$theme->getColourByIndex((int) $color['theme']);
+            if ($this->theme !== null) {
+                $returnColour = $this->theme->getColourByIndex((int) $color['theme']);
                 if (isset($color['tint'])) {
                     $tintAdjust = (float) $color['tint'];
-                    $returnColour = Color::changeBrightness($returnColour, $tintAdjust);
+                    $returnColour = Color::changeBrightness($returnColour ?? '', $tintAdjust);
                 }
 
                 return 'FF' . $returnColour;
@@ -253,7 +277,7 @@ public static function readColor($color, $background = false)
         return ($background) ? 'FFFFFFFF' : 'FF000000';
     }
 
-    public function dxfs($readDataOnly = false)
+    public function dxfs(bool $readDataOnly = false): array
     {
         $dxfs = [];
         if (!$readDataOnly && $this->styleXml) {
@@ -285,13 +309,20 @@ public function dxfs($readDataOnly = false)
         return $dxfs;
     }
 
-    public function styles()
+    public function styles(): array
     {
         return $this->styles;
     }
 
-    private static function getArrayItem($array, $key = 0)
+    /**
+     * Get array item.
+     *
+     * @param mixed $array (usually array, in theory can be false)
+     *
+     * @return stdClass
+     */
+    private static function getArrayItem($array, int $key = 0)
     {
-        return $array[$key] ?? null;
+        return is_array($array) ? ($array[$key] ?? null) : null;
     }
 }
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/ColorTabTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/ColorTabTest.php
new file mode 100644
index 0000000000..2218ace14f
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/ColorTabTest.php
@@ -0,0 +1,22 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
+
+use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
+use PHPUnit\Framework\TestCase;
+
+class ColorTabTest extends TestCase
+{
+    public function testIssue2316(): void
+    {
+        $filename = 'tests/data/Reader/XLSX/colortabs.xlsx';
+        $reader = new Xlsx();
+        $spreadsheet = $reader->load($filename);
+
+        // theme color
+        self::assertSame('FF548135', $spreadsheet->getSheet(0)->getTabColor()->getArgb());
+        // rgb color
+        self::assertSame('FFFFC000', $spreadsheet->getSheet(1)->getTabColor()->getArgb());
+        $spreadsheet->disconnectWorksheets();
+    }
+}
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/CoverageGapsTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/CoverageGapsTest.php
new file mode 100644
index 0000000000..6630a3fe61
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/CoverageGapsTest.php
@@ -0,0 +1,43 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
+
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+use PhpOffice\PhpSpreadsheet\Style\Alignment;
+use PhpOffice\PhpSpreadsheet\Style\Border;
+use PhpOffice\PhpSpreadsheet\Style\Borders;
+use PhpOffice\PhpSpreadsheet\Style\Protection;
+use PhpOffice\PhpSpreadsheetTests\Functional\AbstractFunctional;
+
+class CoverageGapsTest extends AbstractFunctional
+{
+    public function testCoverageGaps(): void
+    {
+        $spreadsheet = new Spreadsheet();
+        $sheet = $spreadsheet->getActiveSheet();
+        $sheet
+            ->getStyle('A1')
+            ->getBorders()
+            ->setDiagonalDirection(Borders::DIAGONAL_BOTH)
+            ->getDiagonal()
+            ->setBorderStyle(Border::BORDER_DASHDOTDOT);
+        $sheet
+            ->getStyle('A2')
+            ->getProtection()
+            ->setLocked(Protection::PROTECTION_PROTECTED);
+        $sheet
+            ->getStyle('A3')
+            ->getAlignment()
+            ->setTextRotation(Alignment::TEXTROTATION_STACK_EXCEL);
+        $reloadedSpreadsheet = $this->writeAndReload($spreadsheet, 'Xlsx');
+        $spreadsheet->disconnectWorksheets();
+
+        $rsheet = $reloadedSpreadsheet->getActiveSheet();
+        self::assertSame(Borders::DIAGONAL_BOTH, $rsheet->getStyle('A1')->getBorders()->getDiagonalDirection());
+        self::assertSame(Border::BORDER_DASHDOTDOT, $rsheet->getStyle('A1')->getBorders()->getDiagonal()->getBorderStyle());
+        self::assertSame(Protection::PROTECTION_PROTECTED, $rsheet->getStyle('A2')->getProtection()->getLocked());
+        self::assertSame(Alignment::TEXTROTATION_STACK_PHPSPREADSHEET, $rsheet->getStyle('A3')->getAlignment()->getTextRotation());
+
+        $reloadedSpreadsheet->disconnectWorksheets();
+    }
+}
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2387Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2387Test.php
new file mode 100644
index 0000000000..870ea6ab04
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2387Test.php
@@ -0,0 +1,26 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
+
+use PhpOffice\PhpSpreadsheet\IOFactory;
+use PhpOffice\PhpSpreadsheet\Style\Fill;
+use PHPUnit\Framework\TestCase;
+
+class Issue2387Test extends TestCase
+{
+    public function testIssue2387(): void
+    {
+        // Theme was not being handled.
+        $filename = 'tests/data/Reader/XLSX/issue.2387.xlsx';
+        $reader = IOFactory::createReader('Xlsx');
+        $spreadsheet = $reader->load($filename);
+        $sheet = $spreadsheet->getActiveSheet();
+        self::assertSame('335593', $sheet->getCell('B2')->getStyle()->getFont()->getColor()->getRgb());
+        self::assertSame(Fill::FILL_NONE, $sheet->getCell('B2')->getStyle()->getFill()->getFillType());
+        self::assertSame('FFFFFF', $sheet->getCell('C2')->getStyle()->getFont()->getColor()->getRgb());
+        self::assertSame('000000', $sheet->getCell('C2')->getStyle()->getFill()->getStartColor()->getRgb());
+        self::assertSame(Fill::FILL_SOLID, $sheet->getCell('C2')->getStyle()->getFill()->getFillType());
+
+        $spreadsheet->disconnectWorksheets();
+    }
+}
diff --git a/tests/data/Reader/XLSX/colortabs.xlsx b/tests/data/Reader/XLSX/colortabs.xlsx
new file mode 100644
index 0000000000..84863ab45e
Binary files /dev/null and b/tests/data/Reader/XLSX/colortabs.xlsx differ
diff --git a/tests/data/Reader/XLSX/issue.2387.xlsx b/tests/data/Reader/XLSX/issue.2387.xlsx
new file mode 100644
index 0000000000..891ee31dbf
Binary files /dev/null and b/tests/data/Reader/XLSX/issue.2387.xlsx differ