Ok, Im no pixel expert, but some suggestions _I_ would try.
The three, I think, would feel god if he got drager forward a little. Unless its a part of the background.
It doesnt seem to be at the same plane/level as the grass, but uts just a little.. (I think)
Things I would try to do this with is either saturate it a little or desaturate the grass.
You could also try to make it brighter highlights.
Maybe change the background color a little to make the character to read better.
Things I like with platformers are whats under the grass, think its as it would be in glass and you will see everything.
I think it adds variation to it..
Just mu suggestions.
Oh btw! the three looks awesome, nice colors and organic shape, maybe a little work on the leafs could be cool.
EDIT: hope you dont mind, I made a little edit with maybe some suggestions.
What I did: Lowered the saturation of grass - slided the characters color alittle against green - Added redish background which work basicly complementary color to blue-green, should make them read. You could even make it darker and the character(who is pretty bright) read Imo... Also tried some lame AA on the three, sorry
Maybe something inspired you.
