This is really interesting to know, I haven't tried to create a game with colors for Gameboy Color yet, so I don't know the limits faced by projects like this. The effect in just 4 colors is great, so using these effects with more colors sounds very exciting.
I took a quick look at your DE '22 game, and it's really well produced, the cutscenes are quite impressive. When I'm done, I'd love to tell you what I thought.