The visuals of this game are quite clean, I think maybe you could either commit to the high res geometric vibe or stick with the background which seems more artistic and layered but still monochromatic, neither seems like it could go wrong. Now to play devil's advocate I do actually think that the "awkward" controls make sense for the gameplay - metamorphosis should have some cost associated with it so you can't just freely switch to the one that best suits you, so the difficulty of having to navigate while morphing is actually a good thing here. There are other ways to potentially add that, like a cooldown between colors, the need to charge up a color before switching to it, locking movement while morphing over half a second, etc. which could all potentially serve the same purpose though. I think this would be a fun infinite arcade scroller - I don't know if the difficulty ramps up or not, it didn't as far as I could tell, but if it did, and after adding in a bit of challenge around the morphing process, it would be pretty zen to play.
Also the sound effect for hitting a mine is REALLY loud. That might be good to turn down or at least allow options for. But that's a minor issue.