I was building a ROM switching adapter so that I could use modern 27256 ROMs in the 2332 and 2364 footprints on the Commodore 64. I decided to add an LED and resistor to the bottom for mood lighting. When I started adding LEDs of different colors it turned pretty sexy pretty fast.

The latest iteration of this adapted has the microcontroller right on the adapter under the 27256. It handles switching the address lines, choosing between 2332 and 2364, and runs the RESET and EXROM lines. I have a pin left that I could use to run a WS2812 programmable RGB LED.