2 things I recommend for the colors, 1) break down the hues a little further to make some of the shapes a little bit distinguishable, 2) adjust the saturation.
Ideally you don't want to have a bright background highly saturated, it is a depth killer. Usually the brighter things are the more desaturated they become. I know most artists are aware how value and hue can affect depth, but don't seem to understand how saturation plays a role in it... I'll try and illustrate it in an overpainting.