[B][/B]How do Shadows & coloring work in an animation, please help a newbie:)

Hi everybody, im new in animation and decided to make a serious animation for my bachelor's final project (anime in fact, each frame hand drawn digitally) . I am studying sound engineering and using the title "Animation & Sound Design production" as an excuse for my project so it would be relative to my degree and still get to work with 2d, which i wanted to do for some time now:)

I am using mostly The tab for my animations and i'm wondering how to color my drawings. Do i do it in the same layer of the main animation drawings, or in a seperate layer?

Also how do shadows work in an animation. Specifically character shadows.
Again i'm confused at what layer it will go to and how to animate them.
Basically i'm confused at what layer goes what.

I'm trying to finish at least a 3 minute short animation in 3 months without a deep knowledge in animation, so i really dont have a life anymore:D , so any help would be greatly apreciated.

Thanks!