My friend Jimmie
turned me on to some excellent color-changing LEDs. There are several kinds of RGB LEDs: the ones with four wires are meant to have their colors mixed by a circuit. The ones with two wires change on their own and can't be programmed. But they are fun and perfect for a project like this. I prefer the ones that change slowly, and Jimmie showed me that you can find these on eBay by searching for rgb slow color change
on eBay. They will take a week or more to arrive, which is cutting it close for this Christmas.