Merry Christmas!
Sparkle Labs published a paper Christmas tree kit (http://kits.sparklelabs.com/2009/12/15/light-up-christmas-tree-project/) that I did on my Craft Robo paper cutter. I lit them up with a pair of ShiftBrite addressable RGB LEDs controlled by an Arduino microcontroller. It’s basically a slightly modified version of the Spookotron Halloween pumpkin lights.
It’s pretty simple but looks good.