store color data (#3134)

Co-authored-by: Benjamin Hackl <devel@benjamin-hackl.at>

Author: icedcoffeeee

manim/mobject/opengl/opengl_surface.py

@@ -261,7 +261,9 @@ def get_shader_data(self):
             shader_data["du_point"] = du_points
             shader_data["dv_point"] = dv_points
             if self.colorscale:
-                shader_data["color"] = self._get_color_by_value(s_points)
+                if not hasattr(self, "color_by_val"):
+                    self.color_by_val = self._get_color_by_value(s_points)
+                shader_data["color"] = self.color_by_val
             else:
                 self.fill_in_shader_color_info(shader_data)
         return shader_data