I learned this techinique in the CAS card class. Basically it's colored pencils on white ink and it really makes the color pop off the dark card stock.
I used my really old Prismacolor pencils that I've had since I was in school for Architecture (a long time ago) and they still work great! I first stamped my images with Stampin' Up! Whisper White craft ink which is a pigment ink and then heat set it. Coloring in on top wasn't as tedious as I thought it would be and I found that if you rotate the pencil as you color you won't have to sharpen the point as often (drafting tip from the old days of doing Architecture drawings by hand - dating myself again!)
Anyway, here's my version of Jennifer McGuire's card...
card stock: SU Naturals White, Basic Black, So Saffron
stamps: SU Raining Flowers, Hero Arts All Occassion
Ink: SU Craft whisper white
Button: SU Rich Razzleberry
Other: DMC Floss