Cartoonist Brian McLachlan has posted an amazing write-up on coloring comics.
This how-to-colour-comics tutorial is geared towards webcomics but applies to regular comics as well. I’m not going to teach you the ins-and-outs of a particular art program. Instead, you will learn 10 important things to consider whether you colour with Photoshop or a paintbrush. These lessons will keep your comic storytelling clear and dynamic.
He breaks it down to 10 main points. Read vs real, basics of colour theory, RGB vs CMYK, character design, sketch from life are some of what he covers.
So head on over and check it out.