I am somewhat skeptical, though open to the idea of the buttons being painted. Part of the problem I see, however, is that the buttons on an original MQ-1 are a very reflective metal/silver color and could be any of those colors while tilted at various angles.
Well, since the keypad in the "carbonite chamber" pic is pretty straight-on, and the buttons are decidedly different shades at least, they may have been different colors. It's hard to tell, though, because of the orange gradation of the pic, which colors they might be.
If they are different colors, then they are certainly in a different color arrangement than the colored ROTJ keypad buttons.
The buttons seem to have caught the flash in that picture. But it does still look like there is a slight red/yellow glow around the 1st two rows (on the left if you were looking at the keypad straight on and right way up) and more of a blue glow on the rest of them.