It's rare that I sprite..

[Jovian-12]

if you're going to keep that color scheme, the shading needs tweaking. it needs to stand out. the yellow should probably be shaded with something more orangey and the cyan something more blue. not extremely so; I don't want to see you shade them with exactly orange or blue (cuz that would look just as bad), but adding a bit of another color to the shading makes it pop out.

plus dark yellow looks disgusting and dark cyan is tealish.