This is an old technique that is making a real comeback. Back in the day, SU demonstrator Karen Barber made some beautiful cards with this technique called "Black Magic" and she has some recent ones on her blog as well so give her a visit and scroll around. Black Magic involves stamping your image on a dark card stock (black, deep brown, blue or burgundy) -- you stamp with White pigment ink, let it dry (you can speed the drying with a heat tool, but it is not embossed). Once it's dry, you add color over the white with colored pencils (I used SU's watercolor pencils on mine) plus I even used watercolor crayons on my sample, they work great and they are a perfect match of course for SU card stock colors. FYI -- the little bit of coloring outside the lines that you can see in the photo is not really visible with the naked eye. Adding accents with a white gel pen steps it up a notch.
Here is a beautiful card using this technique made by 3-2-1 Stamp team member Beth Daniels. She got the inspiration to stamp over the script stamp from Donna Centamore (isn't sharing with others so much fun?) I love that about stampers. Be sure to let the layer that is the script background dry very well before you start coloring so you don't smear any ink.
I used the Watercolor Trio set from the Summer mini catalog on my sample -- it even includes the wonderful greetings and three flower stem images -- all perfect for this technique. The card layout was copyed right out of my Stampin' Success magazine that's just for demonstrators.The background is Sahara Sand, with Garden Green embossed with the Square Lattice Embossing Folder from the SU summer mini as the mat.
FYI -- if you've ever been a Stampin' Up demonstrator, but have not been active since March 31 of this year -- watch for an amazing welcome back deal coming July 1. You can re-sign up for a song — and I mean an amazing kit offer that is just $35 — you read that right (they know you already own lots of crafting goodies so they can offer a mini kit with just the business basics)! If you were a 3-2-1 Stamper before I'd love to have you back on our team. And if you were a demo but have no active demonstrator that you work with anymore, get in touch and I can get you all the info.