here is a look at my coloring technique. as you can see i tend to block in very flat colors and let my line work and shadow shapes help define the three dimensional forms. you can get a lot of dimension just by adding a tone layer as well as a highlight layer. also i add a scanned in texture of tea staining to help add a watercolor-ish feel and i find it helps take some of the digital feel away from the piece. this was painted in photoshop cs6.