Ever wanted to do a colored pencil illustration on dark paper? Most colors generally won’t show up on a darker medium but you can use this guide to trick the system instead. Just draw on white and invert the image to get the colors you originally pictured. So, here’s the guide —

how to color on black
1.  Find the color you hope to achieve in the inverted image (on black).
2.  Look to the corresponding square in the original image (on white).
3.  Draw with that color on your white or lightly colored medium.
4.  Repeat, etc, finish drawing…
5.  Scan, load to Photoshop, rasterize layer, and go to “Image” -> “Adjustments” -> “Invert”

Voila!

To get really accurate results based off this key — I made it with the 72-pack of Prismacolor soft-colored pencils (which I could not recommend more!) with colors ordered as they are in the insert included with the pencils. Or, you can just email me if you want to know the exact name/hex#/etc of any of these colors.

EDIT: Tested out this little tool with an abstract drawing here.