Ticket #3599: 3599.patch

_source/plugins/colorbutton/plugin.js

@@ -223 +223 @@
 CKEDITOR.config.colorButton_backStyle =
         {
                 element         : 'span',
-                styles          : { 'background-color' : '#(color)' }
+                styles          : { 'background-color' : '#(color)' },
+
+                // It's better to apply background color as the innermost style. (#3599)
+                childRule : function( element )
+                {
+                        return false;
+                }
         };