It's very good for your first skin, very good indeed. However, there are a two things I'd advise doing.

First of which, is adding more colors to smooth the transition between light blue and dark blue, dark skin and very dark skin, et cetera.

Second, would be shading as to make the more visible parts of the skin bright (for example, back, sides and front), and making less visible parts of the skin dark (for example, armpits).

But overall, very superb skin.