We picked up a kind of neat pumpkin with a color changing LED in it. However it was just a standard Fast Fade LED of the kind that you buy on eBay (in fact I have some in the lab that are exactly the same shift pattern) and the pattern was disliked by all as it does a lot of flashing, not so much with the fading.
I grabbed an ATTiny85 off the shelf, wired an RGB LED directly to the PWM outputs (no resistors needed because of the internal resistance of the batteries), whipped up some quick code for it, got the color shifts about where we wanted them, and threw it all on a small board that replaced the single self-flashing LED on top of the existing battery holder/switch and hot-glued it in the pumpkin again.
Here's the board pre-install and the completed thing:
Click here for the code.