A while ago I bought a set of pan pastels (the same as normal pastels but in a plastic cup rather than a stick). It was a must-have buy at the time, but I never really used them. In the spirit of investigation, I photocopied a drawing from my sketchbook onto normal printer paper, and used the pastels with their sponge applicator to add colour over the print.
I quite like the effect! And it was very simple and quick to do.