Spoilers:

The trick was pretty easy to guess but still a lot of fun to see put into practice. The EGA monitor bits, and more broadly just the idea of trading color bit depth to multiplex signals for multiple monitors into a single framebuffer and physical output is pretty cool. The Windows display driver idea actually implemented on real hardware would be tons of fun. I could have seen products actually doing this "back in the day" to do multi-head setups. I'm kinda surprised examples don't exist.

Could you accomplish something similar with just colored foil? Like, red foil makes red and white look the same.