There's not really much to critique here and comments that don't have important things to say are frowned upon in this forum, so that (and just bad luck I guess) is why you don't get comments
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Color choices for the blue part aren't bad. Good contrast and amount. The grey on the other hand is very low contrast, and I don't think you actually need all three of those colors.
Also, it's a flat object so it wouldn't be shaded like that. It would have circular lighting instead of this concave stuff you have going on now, because as the light gets closer to the lightsource it gets lighter, and as it is now the shadows are kind of radiating out from one point, which is what light, and not shadow, does.
