I have a beginners photoshop tutorial in my gallery, but for other stuff I suggest you look at my tutorial folder in my favorites. It's filled with the most useful tutorials I've found. Many are about coloring. By coloring I'm assuming you mean blending is what you're having difficulties with? and not cell shading which is very simple and almost self explanatory.
Once you get the feel of it, the best thing to do is loose sketches. Then try drawing different types of lines using the pressure sensitivity as much as possible. I don't really understand what you mean about your difficulty colouring, as that's a pretty basic thing? Fill the area with colour then shade it. Look at some tutorials, I can't give too much help with that as it's a personal thing.