Funnily enough, I actually did use a color palette. I think because the palette was a bit bigger, and I only used 2 colors per sprite, the visuals still didn't get the coherency that a palette usually helps with. I also would have liked to have included music in the levels, but I feared that it might cover up being able to hear a switch being pressed off-screen, and that wasn't a problem I expected to have the time to find a solution for. If/When I continue development, I'll have to see if that does become an issue with level music, and maybe implement some sort of visual indicator to make up for it.
Thanks for your feedback!