[Tom] has been refining a board that drives a high power RGB LED for applications like this moodlight. It’s based around an ATmega8 microcontroller. The goal was to make an RGB LED easy to work with: It can cycle between colors in standalone mode. You can control it via a serial interface. It also has a pin header to hooking up three potentiometers for manual color mixing. Boards aren’t available yet, but he’s already posted a build tutorial. The board looks straightforward enough that it shouldn’t be too hard to layout if you really want to.