It's a common anode RGB LED light that transitions between several colors. I'm using my T85 Target board. Information of the board can be found here which includes all the details about it plus links to the gihub page for the board file if you want to make your own.
This project uses the AVR-GCC toolchain. The compiled hex program is under 1 kB in size as required for entry into the HaH 1kB challenge. I verified this using the avr-size command.