I concur with Blood Lord. Ari's a beast at coloring. Really, he's good at cel-shading.
There’s some color bleeding on the scarf, jacket, and shoes. Try to stay within the lines, unless you want to try something out like radiosity
. But if you are, then you’ll need some better understanding on how light interacts with the form and its surroundings.
Speaking of form, Ari’s right about your figures needing more work. You might want to pin that down before tackling color, since your coloring is going to be based on what you put down on paper. You don’t have to get super duper good before coloring, just enough so you have a sense of where things belong and how light will work.
Here’s this tumblr tutorial
on how to get started on drawing from reference. Simply put, look at things and copy it. Too hard to copy? Break it down to its basic shapes: circles, squares, and triangles. Trace if you have to, but as the tutorial says, that’s just for practice. Don’t claim it as your own!
Aaaas for coloring…Ah gee this one is a huge topic.
Ari laid down a nice foundation in his post: various darker colors for shade, lighter colors for highlights. As for where do those shades and highlights belong? The easiest way to determine this is just to get a feel for it and look at as many references pictures you can find. Obviously, areas closer to the light are lighter, areas away from the light or covered are darker. Different shapes will cast shadows and reflect light differently (haha redundancy is my middle name). Here is what I’m getting at
Notice the shadows on the shapes? They’re not hugging the lines. Keep this under your cap.
I would drop off many more a links, but my time’s almost up for now. So, happy art-ing, keep up the work, practice, and importantly, have fun and don’t be afraid to ask or something. This goes for whoever else stumbles upon this post as well.