This is a really cool, simple concept. I think it would benefit a little from some feedback on when you get the color right (for a while, I wasn't sure if I actually succeeded after pressing space). Also (this might just be my browser), but when I pressed "up" and "down'", the browser would scroll in addition to changing the saturation, which made it a little tougher to play the game.
I'm not great with colors, so this game was definitely a challenge for me haha. Again, I love the simplicity of it. Check color, iterate, check color, iterate. Definitely satisfying to play. Nice job!