This question instantly reminded me of a debate I had with a friend in high school math club 😂 We were trying to color a fictional map for a project and got into a whole rabbit hole about the four color theorem. We ended up testing it ourselves with handmade maps and markers, and I swear it made me appreciate how complex ""simple"" things can be. Funny enough, that’s also when I got into stress-relief coloring pages—I needed a break from all the graph theory headaches. Still use them sometimes when I want to clear my head. It's a fun way to relax and secretly keep thinking about colors and patterns, haha.

Are you asking for the minimum number of colours for all arbitrary biplane graph, or the minimum number possible for a single biplane graph (which I think would be 2)

@CromlynGames The former.