The colour of the cat looks fine to me. It might not be as grey as it should be, but I don't think it's that big of a problem. The colours of the rainbow could be better though. The yellow doesn't look yellow at all, and there isn't much distinction between the orange and the red. If there isn't much that can be done about it though, I think the keys look good enough!
I think if possible, the yellow should be fixed, if nothing else.