FROADER is out cutting up some powder so I guess I'll pretend I'm him for a bit.
Okay so we're going to start off with a Smart car here, dark blue oh yeah.
1) Do the usual selection of the body you want to change color.
2) Press
CTRL+M, which brings up the Curves window. Bend the curve up so that the vehicle's body looks fairly light. Make sure none of the curve ever touches the very top of the graph (except for the point on the far right) or else you will loose pixel information and will make your image look wack. So the curve should look something like this (again, none of it should be at the very top of the graph.
3) Once you're done with the curve, hit OK and press CTRL + U, which brings up the HSB window, or Hue Saturation and Brightness (aka "Lightness") and play with the three sliders to your liking. Hue changes the color, Saturation changes intensity of the color, and Lightness of course changes how light/dark the color is.
4) Hit OK once you're happy with the result. And here's what Burns' Smart car would look like
