We can make a character and his/her clothes any color we want in any which way. We can make practically any weapon we want, in any color we want. We can make custom graffiti even. BUT, can we in any way whatsoever edit the colors of a musical instrument in the game? (Because as you all know, I love colors.)
So, no, it's not possible with how the game calls the instrument item. The item ID refers directly to the .instrument file which then calls the image file, so without having direct access to the image file, it would not be possible to do a color substitution. Now, what we /could/ try, is to add a variable to the item within StarCheat and have the variable call the instrument image directly, possibly as an overlay to the one that is already there. This way, we could re-color the overlay. I'll try this when I have more time.
It looks like the instrument items ignore any additional attributes like 'Drawables'. Not sure this can be done, but will keep doing science to find out.
