For a simple color conversion it seems to be a good choice to use the easy mode for editing the CSS instead of the advanced mode. But I'd like to suggest some improvements.

Not all background colors are recognized:
Most background colors in the default stylesheet are definded by "background" rather than "background-color" entries, but the easy mode only recognizes "background-color" entries. There are two approaches to fix this. Either you could provide a stylesheet that always uses "background-color" or you could advance your parsing script to recognize colors also in "background" entries. The latter would be the better way, because people wouldn't have to update their CSS in custom skins.

Border colors aren't recognized:
It would be great if the easy mode also showed the border colors. Then all color entries would be shown in easy mode.

I agree with this suggestion. I would also like to see the CSS Easy Mode go more in-deapth and recognize all the CSS color properties.

Ali