Check out Fancade. It's genuinely the best mobile "game engine" to this day imo. It has a full blown 3d voxel-based editor and a unique and fun visual scripting system
Changing colours should be fine, as long as there are only 2 on the screen at a time
Well, if the engine allows you to export the game for PC as an executable and/or for web, then you are most probably allowed to use it for your game!
