REDDER is a game by Anna Anthropy / Auntie Pixelante, with music by Amon26. It’s an exploration platformer focused around an alternating green/red block switch mechanic, similar to the mechanic used in the third pendent dungeon in the SNES classic A Link to the Past.
I found the colors very nice (even though the backgrounds are often just gradients, there’s a lot that can be done with just gradients of color), and the exploration of a fairly large world excellent. In a few ways the game resembles VVVVVV, but only in basic structure: a world of screen-sized rooms, numerous checkpoints, things to collect, but is more non-linear, slower-paced, and not as focused on challenge (you won’t die very often if you’re decent at platformers).
I’ve played through many of her other games (When Pig’s Fly, Calamity Annie, Mighty Jill Off, Invader), and so far this one’s by far my favorite; maybe you guys will agree.