I was visiting the deviantART website and came across Mike Hawthorne's work (he's currently doing the Conan series with Roy Thomas) Anyway, I came across a cool Plastic Man and Catwoman drawing, and was trying to figure out how to color his linework. Here's his, and then my flat colors on his. I'm not much of a colorist, so I was curious how one would add the depth colors.

Start by using "cell shading" -- add dark versions of the colors you're using where shadows fall in the piece. Here's a quick, sloppy example using the burn tool -- obviously, you'll do a much nicer job than this.

Layers are a big help too. Are you using Photoshop?

I tend to use Paint Shop Photo Pro. It has layers as well.

Yeah, I don't advise you to use the Burn tool overall -- I was just using it because you had the colored piece all in one layer. Use the paintbrush when possible.

Also, don't forget highlights -- I just added shading in my example because it was on-the-fly and a quickie thing to illustrate a point.

Sometimes I'll use the burn tool to see what shades work. Then pick that shade with the eyedropper and undo the burn tool.

And if I do leave the "burn" in there, usually I'll have to adjust the saturation for that area, so that it looks less burned. So I rarely go with the burn.

For me, burn tool should just be a minor touch-up tool in most cases.

I prefer the Byrne tool.

Automatically seats your subject in a cahir and gives them an O mouth.

Byrne tool? That's redundant.

It's an oxymoron you oxy-moron.

The quickest and easiest way to do coloring is to add a layer over the original, and setting it to 'multiply'. That gives you a layer for the color only so you don't have to worry about messing up the line art.
Here's a quick example:
Line art:


Color layer:


Combined:


The process differs from person to person, as does the complexity of layers, etc. but there are tons of tutorials online that will give you some great tips.

One bit of advice, choose your colors wisely. Try to stay away from the 'in your face/florescent/oversaturated' colors. For example if you are coloring the Hulk, remember he's green, but not super-mega burn your retinas green, not is he dark as the darkest Belgian forrest green either.. find a pic you like, and try to choose a shade that fits. (the color picker/eyedropper tool is perfect for that.)

Again, I've never been a master at painting. I know I can do line art, whether it's pencil or pen, but when it came to coloring... bleah. Anyway, this is what I ended up with based on my base talents and skills.

HEY!
There you go!
The only thing I'd suggest is some highlighting with lighter colors on some of the surfaces. That'll give it some added depth/dimension.

I figured that. Any suggestions on any of the surfaces to highlight? I know that it needs it, but it's not "natural" for me. And THANK you for the help.

Basically Mark, the light goes opposite the dark. You have darkened the bottom of PM's torso (his left). I'd lighten the top of his torso (his right). Basically, by the way you chose to highlight, the light source for this picture is shining almost straight down, so use that to figure where the highlights would go.

This model pretty much covers the whole concept.

Must be noon, which is why it was so easy for him to wrap up the case.

Ok. This is what I have.

A little too bright on the highlights, but looking good.

Ok... I edited it dropped the highlights down, and when I posted it here, it seemed even brighter. Weird.