When I was photographing my 1st finished Tau Tank, I figured I take it into Photoshop and play with the Hue. I use photoshop all day for my work and actually never thought about it before. I made a short (and clumsy) video of it: check it out
The way to get to the hue is CTRL-U
Of course this method is kind of funky, since you need a painted model to begin with, but you could download an image from the web, import it and start playing. I personally think the orange brown one (when the slider was to the left) looked really interesting..
anyway, hope you think it is helpful!