For those who use Photoshop for postwork, a great way to change the color of something (background, figure, whatever) is to create a new layer and fill it with a solid color.  A light gray/silver is ideal for giving your humans a more natural skin-tone.

Here's a step-by-step on how to do it (pictures will come later...)

1) Create a new layer
2) Fill layer with light shade (light gray/silver)
3) Change Layer Setting to something like "Color dodge" or "Color Burn".  (or you can just go through all of them until you find something that you like).

If you only want your figure to change, and not the entire scene, you'll have to select that figure.  My suggestion is to have a seperate layer for each figure/object in the scene.  Using the "Devil Angels" pic as an example, have the "Angels" as one layer, the "Devil" as another, and the background as yet another layer.  That way you can just click on the layer with what you want, which will select it, go to Select>Inverse and delete on the filled layer.  Voila!  Now you have a layer with just the layer shading you want.  Just repeat the process for the other layers using the same color or vary it.

I'll post pics later of how to do this, but its pretty simple.