It's also a fun one to write an emulator for. There are plenty of example programs out there to test, and they draw graphics by writing bytes to a frame buffer at some offset in memory. You can read from that region in memory, interpret each byte as a color from a preset palette, and use it to display visual output / graphics.

I wrote one in Swift a few years back, and then ended up developing it further into an NES emulator capable of playing Donkey Kong. It was a great learning experience.