Looks good. For an outdoor scene, the subject looks terribly dark, although if that's a stylistic choice (like in Renaissance paintings) then fair dos. When it comes to shifting hues, you should have a think about doing so in context. For example, since he's sitting on a blue object, part of which is lit with sunlight, I'd think about mixing some blue into the shadow tone of his legs, arm and feet. Because the blue object is illuminated in the way that it is, you should treat it as another light source, albeit a weak one, but still strong enough to influence the tones of near by surfaces. In the same way, the blue sky can be considered as yet another light source, and in fact you've already done this with the leaves and clouds' shadow.
I really like the little tree hair and the idea itself. If you continue with the background I'd do something to distinguish it from the foreground, perhaps by making it lighter or my personal favourite: depth of field blur.