How do you make your gradient colors contour a pre drawn picture in Photoshop? I have some black and white sketches that I am trying to put a gradient color going alone the contours of the outlines, but I can’t find a way to get it to do that. They layer styles don’t help since they have their own format which I don’t know how to edit and it doesn''t allow me to flood in a spot. The old art programs use to do these things easy and it’s hard to believe that you can’t do it now. The manual doesn’t help. If you can help, thanks.

Image->Adjust->Gradient Map...