Now comes the colour. I won't go into a great deal of detail as it's pretty straightforward for anyone who uses Photoshop. What I have found is useful is to create a layer of just flat colour using the Lasso Tool and Paint Bucket and duplicate this into a safe area so that when if comes to either shading or applying filter effects you can just use the magic wand tool to select the area you want to alter.
With the classic comic idea in mind I used the photoshop filter Pixelate -> Color Halftone to give it that comic/pop art look of the little dots. You have to play around with the settings until you get the effect your looking for.
I added the comic logo (based loosely upon the Marvel comic logo) and a spoof of the Comics Code logo that was prevalent around the 70's.
As an after thought give it a slightly vintage look, as if it were an old and well read comic book, I added a layer of old paper scanned in and used a layer mask to just reveal enough to "age" the drawing.