Did a little poking in Launcher with ResEdit.
It looks like the resource — mashs
contains color information, but I didn't try anything.
This calls for the obligatory ResEdit disclaimer:
Always work on a copy of whatever file you are modifying, that way when you screw up, and eventually you will, you won't trash your entire setup. Don't try this if you are not comfortable with it. ResEdit is a powerful, even if long-in-the-tooth, utility and you can do serious damage with it, even if you do know what you are doing.