11
As Tara said, you don't need to know how to draw to color. Just get out your Quick Selection/Magic Wand tools (not to mention the Rectangular Marquee Tool for hard-to-get places), select, select, select, set the layer to Multiply, make a new layer below, fill with the color you want, and poof! You have a simple colored part. To make it more complex, you could follow tuts. for shading, but I just Gaussian Blur once and it comes out all right most the time.