Change "perceive color" to be more accurate

understanding/20/use-of-color.html

@@ -56,8 +56,8 @@ <h2>Intent of Use of Color</h2>
             Similarly, if content is distinguished by inverting an element's foreground and background colors,
             this would pass (again, assuming that the foreground and background colors have a sufficient contrast).
          </p>
-         <p>However, if content relies on the user's ability to accurately perceive a particular color (either
-            implicitly - e.g. green for success, red for failure - or explicitly - e.g. "the blue items represent
+         <p>However, if content relies on the user's ability to accurately perceive or differentiate a particular color
+            (either implicitly - e.g. green for success, red for failure - or explicitly - e.g. "the blue items represent
             the most recently updated entries"), an additional visual indicator will be required, regardless of
             the relative contrast between those colors.
          </p>
@@ -67,7 +67,8 @@ <h2>Intent of Use of Color</h2>
       <div class="note">
 
          <p>This criterion does not directly address the needs of users with assistive technologies.
-            It aims to ensure that sighted users who cannot perceive color can still understand content.
+            It aims to ensure that sighted users who cannot distinguish between some colors can still
+            understand content.
             How information is conveyed to assistive technology users is covered separately in other
             criteria, including (but not limited to)
             <a href="non-text-content">1.1.1 Non-text Content</a>,
@@ -76,8 +77,8 @@ <h2>Intent of Use of Color</h2>
          </p>
          <p>Conversely, even if information that is conveyed by color differences is appropriately conveyed
             to assistive technologies, it does not necessarily pass this criterion, as sighted users who cannot
-            perceive color may not necessarily be using any assistive technologies. This criterion requires
-            a visible alternative to color.
+            distinguish bewtween certain color may not necessarily be using any assistive technologies. This
+            criterion requires a visible alternative to color.
          </p>
 
       </div>
@@ -144,7 +145,8 @@ <h2>Examples of Use of Color</h2>
             <p>Students view an SVG image of a chemical compound and identify the chemical elements
                present based <strong>both</strong> on the colors used, as well as numbers next to each
                element. A legend shows the color and number for each type of element. Sighted users who
-               cannot perceive color can still understand the image by relying on the numbers.
+               cannot perceive all the color differences can still understand the image by relying on
+               the numbers.
             </p>
 
          </li>