PINK & YELLOWI would not recommend anyone trying this unless using a really cheap keyboard and have at least a little experience taking things apart and putting them back together successfully.
That being said... I decided to take apart my Yamaha MM6 to custom paint it. The project took me about 8 hours total and I had a few hiccups along the way, but in the end I worked out the kinks and ended up with a pretty sweet lookin' keymachine.

Before I had the circuit board completely disconnected from it's casing, I made sure to make a map of where all the buttons go and their functions, so I could make sure to put everything back where it belonged.
I spray painted the individual parts different colors, and then used lace and other screen-like materials to spray patterns on top of the solid layers of color.. I will have to make my own stencils and experiment with this more in the future.

After a long day of work, I managed to get all the pieces back together and turned it on for the final test...and it worked! I still use this keyboard and it has been functioning normally. The only thing I would have changed was adding a clear coat of finish on top of all the final layers.
FINISHED PROJECT::