Allow "color_ThemeName_palette" in variable table to be rebuilt when rebuilding theme

Clearing the cache or even using the devel module to rebuild a theme on every page load will not rebuild this variable. This is probably only an issue when developing complex themes. In my case I created a large number of colors to be settable by the user and I decided to order the colors alphabetically after the list got quite long. However, no matter what I did I could not get the customizable colors to show up alphabetically until I manually removed that variable from the variable table.

I think it should be deleted and recreated anytime someone rebuilds a theme.