Well I think that the anatomical definitions is very well done. You are good with the human face. Her posture is done beautifully, I love how you choose to draw a thin woman, so that her muscles, and some bones details would be accomplished, and so you have. A job well done
I like the result, but, in my opinon, the grey of the dirty pencil get the coloring dirty. In a simple illusration with no background, that is ok, but I can imagine a full illustration or a comic page, and I think you will have to manage it to get it clean. I think doing nice colors in very important parts (for example, woman skin) is important. Ofcourse, it is only my opinion.
The coloring style between cell shading and something ellse is very well compensed. I like the little spots where the color shine, and your knowledge of anatomy is excellent, I love how you did the arm muscles, they are looking awesome.
but the work is looking awesome! As a sketch is fantastic! I sometimes change the color of the line. I do dark red lines in cases like this. Ofcourse, the line can be painted according to the scene, but a usual light day scene, red lines works for me. Dark red, almost black, but not black
Yes, for sure, black or too many thick line in BG is looking bad, couse it erases the deep sensation. I am trying it, just erasing the line in BG, or, if it was a comic, just doing it in a softer color or in a very thin style. But it also depends on the kind of coloring. Now, there is a style that is very strong, and it really needs line to survive. I'm talking about styles like "adventure time". I would like to go in that direction for my style of coloring, but when I have things painted like that, I feel that a lot of things needs to be more painted. I can't relax my mind.