How can I learn by myself how to color comics with a computer graphics software?

I have all kinds of drawings, sketches and comics I drew in black and white by hand. I would like to scan some of them and perform professional coloring on my computer.

I would like to know what computer graphics software should I use and where you can learn it, maybe some books that deal specifically in this field. I once saw a cartoonist using a very interesting software to do that, with color layers and all kinds of affect.