Something obvious that rlly changed the game for me is to use overlays! If you look at old art of Cey, her color scheme is a bit everywhere— her wings have a greenish tone, then her skin is orangey, gray is also greenish, and her eyes are a bright reddish brown. The colors looked much better together once I put a purpley-pink overlay on her! As someone with no art-training, I know very little about color theory and this helped me xD