diff --git a/Arrangement_on_surface_2/demo/earth/Geodesic_arcs.cpp b/Arrangement_on_surface_2/demo/earth/Geodesic_arcs.cpp
index fa68fd9795a..1031eecac74 100644
--- a/Arrangement_on_surface_2/demo/earth/Geodesic_arcs.cpp
+++ b/Arrangement_on_surface_2/demo/earth/Geodesic_arcs.cpp
@@ -85,27 +85,13 @@ Geodesic_arcs::Geodesic_arcs()
       cout << *it << endl;
     cout << "num points output = " << v.size() << endl;
   }
-  
-
-  //const float c = 0.0;
-  //std::vector<QVector3D> vertex_data {
-  //  QVector3D(0,0,0), QVector3D(1,0,0),
-  //  QVector3D(a,0,0), QVector3D(1,0,0),
-
-  //  QVector3D(0,0,0), QVector3D(0,1,0),
-  //  QVector3D(0,a,0), QVector3D(0,1,0),
-
-  //  QVector3D(0,0,0), QVector3D(c,c,1),
-  //  QVector3D(0,0,a), QVector3D(c,c,1)
-  //};
+ 
 
   std::vector<QVector3D> vertex_data;
-  const QVector3D red(1, 0, 0);
   for (const auto& p : v)
   {
     const QVector3D arc_point(p.dx(), p.dy(), p.dz());
     vertex_data.push_back(arc_point);
-    vertex_data.push_back(red);
   }
   m_num_arc_points = v.size(); // CAREFUL: not size of vertex_data!!!
 
@@ -136,16 +122,16 @@ Geodesic_arcs::Geodesic_arcs()
                         position_offset);
   glEnableVertexAttribArray(position_attrib_index);
 
-  // Color Vertex-Attribute
-  GLint color_attrib_index = 1;
-  auto* color_offset = reinterpret_cast<const void*>(3 * sizeof(float));
-  glVertexAttribPointer(color_attrib_index,
-                        3,
-                        GL_FLOAT,
-                        GL_FALSE,
-                        stride,
-                        color_offset);
-  glEnableVertexAttribArray(color_attrib_index);
+  //// Color Vertex-Attribute
+  //GLint color_attrib_index = 1;
+  //auto* color_offset = reinterpret_cast<const void*>(3 * sizeof(float));
+  //glVertexAttribPointer(color_attrib_index,
+  //                      3,
+  //                      GL_FLOAT,
+  //                      GL_FALSE,
+  //                      stride,
+  //                      color_offset);
+  //glEnableVertexAttribArray(color_attrib_index);
 
   glBindBuffer(GL_ARRAY_BUFFER, 0);
   glBindVertexArray(0);
diff --git a/Arrangement_on_surface_2/demo/earth/mainwidget.cpp b/Arrangement_on_surface_2/demo/earth/mainwidget.cpp
index 20086bfc796..2bf065eae0b 100644
--- a/Arrangement_on_surface_2/demo/earth/mainwidget.cpp
+++ b/Arrangement_on_surface_2/demo/earth/mainwidget.cpp
@@ -116,6 +116,7 @@ void MainWidget::init_shader_programs()
 {
   init_sp_smooth();
   init_sp_per_vertex_color();
+  init_sp_arc();
 }
 void MainWidget::init_sp_smooth()
 {
@@ -130,6 +131,12 @@ void MainWidget::init_sp_per_vertex_color()
   const char* fs = "shaders/color_only_fs.glsl";
   m_sp_per_vertex_color.init(vs, "", fs);
 }
+void MainWidget::init_sp_arc()
+{
+  const char* vs = "shaders/arc_vs.glsl";
+  const char* fs = "shaders/arc_fs.glsl";
+  m_sp_arc.init(vs, "", fs);
+}
 
 
 std::ostream& operator << (std::ostream& os, const QVector4D& v)
@@ -183,7 +190,7 @@ void MainWidget::paintGL()
   {
     glDisable(GL_DEPTH_TEST);
 
-    auto& sp = m_sp_per_vertex_color;
+    auto& sp = m_sp_arc;
     sp.use();
     sp.set_uniform("u_mvp", mvp);
 
@@ -196,6 +203,8 @@ void MainWidget::paintGL()
     const auto cos_beta = sin_alpha;
     const auto p = (r * cos_beta) * n;
     QVector4D plane(n.x(), n.y(), n.z(), -QVector3D::dotProduct(p, n));
+    const QVector4D red(1, 0, 0, 1);
+    sp.set_uniform("u_color", red);
     sp.set_uniform("u_plane", plane);
     m_geodesic_arcs->draw();
 
diff --git a/Arrangement_on_surface_2/demo/earth/mainwidget.h b/Arrangement_on_surface_2/demo/earth/mainwidget.h
index 208f14e8c27..0ed2b768563 100644
--- a/Arrangement_on_surface_2/demo/earth/mainwidget.h
+++ b/Arrangement_on_surface_2/demo/earth/mainwidget.h
@@ -47,6 +47,7 @@ class MainWidget : public QOpenGLWidget, protected OpenGLFunctionsBase
   void init_shader_programs();
   void init_sp_smooth();
   void init_sp_per_vertex_color();
+  void init_sp_arc();
 
 private:
   // Objects in the scene
diff --git a/Arrangement_on_surface_2/demo/earth/shaders/arc_fs.glsl b/Arrangement_on_surface_2/demo/earth/shaders/arc_fs.glsl
index 8f42e2c2150..216de00c8d3 100644
--- a/Arrangement_on_surface_2/demo/earth/shaders/arc_fs.glsl
+++ b/Arrangement_on_surface_2/demo/earth/shaders/arc_fs.glsl
@@ -1,7 +1,7 @@
 
 #version 330
 
-uniform vec3 u_color;
+uniform vec4 u_color;
 uniform vec4 u_plane;
 
 
@@ -14,5 +14,5 @@ void main()
 	if( dot(u_plane, vec4(v_pos, 1)) < 0 )
 		discard;
 
-	out_color = vec4(u_color, 1);
+	out_color = u_color;
 }
\ No newline at end of file