Not trying to be rude or snarky, but I don't think shading should be your main focus right now. I'd say work some more on faces and perspective, because in page 4 I'm having a bit of trouble understanding where things are positioned (also, I think she should see a chiropractor because I think she's got some severe scoliosis). Anyways, a great black and white comic is still way better than a "bad" colored one. So keep at it :)