I saw an instruction piece on Derwent's website using metallic colored pencils on black. I don't have any metallic colored pencils, but decided to experiment. I used white watercolor pencil first and did the complete outline and shading.
I then used colored watercolor pencil over the white, letting the white shade it. I added some water using a waterbrush and it just moved the color around. So I let it dry and then added pastel chalk pencil color to it. I just kept layering it until I achieved this result. Not the best, but it is on a 100# drawing paper. For working on that paper, I think I got a good result. I probably should try the same on a Canson or Stonehenge and see how it works. Actually I bought a new Dylusions black journal at Blue Twig Studio and maybe I should open that and try it out! I will keep experimenting.