I am sure there are those that could be of much more assistance here, but basically there are a couple of ways you can go about it.
- adjust the texture itself in an image editing program like photoshop etc, (make sure you save it as a copy or elswhere)
2)adjust the diffuse &/or spectral colours of the skin in the material room.
ideally you can combine both of those methods.
lastly you can also tweek the rgb values of the lights to emphasize what you want to show. if you make a red skin, turn the green down a little for example.
I am sure you will get superior and more detailed advice than this, but its a start.
fugazi1968 beat me to it ;-)
