There are probably numerous limitations to what can be done based on how the game is coded, like if any two characters share a palette, changing one color might look great on one character and make another look like a garbled mess, or there might only be so many palettes to work with that are shared between certain environmental elements and characters so that changing anything will make the entire world look like garbage.
Probably because filling things with a paint bucket in an image editor is a completely different thing than working with pre-coded palettes in a gamebody game. Why not do colors like I done with Paint to give an example?
