The specific request was for how I coloured Lara's shoe in a previous pic. It was as easy as piling up selections and airbrushing some colour in. The comic books I mostly see this done in are the ones coloured by Liquid! and the technique can work pretty good if you mess with it enough. The best examples of Liquid! work that I know of are in BattleChasers.

In this example I decided to do something real simple and so just drew a piece of armour like maybe you would find on a shoulder/upper arm rig. After scanning the pic into photoshop I just used a plain fill of dark grey for a base tone. You could probably use a gradient for the base colour as well but don't vary the colours too much. Then using a lasso selection tool just create whatever selection shapes you want and airbrush (or fill) in an lighter colour. Just continue to do this until you get the look you want. Pretty much all comic book colouring seems to be done using variations on this idea. It comes in handy when a simple gradient fill just won't give the detail you want... any questions? Jason