This is one of my favorite techniques for creating backgrounds to stamp on. I used several colors here (all Twinkling H2O's):
Ginger Peach (upper left corner)
Hot Cinnamon (upper right corner)
Moss Green (left side)
Plum Blossom (right side)
Passion (tiny bit of the lower right corner)
Start with a sheet of 140 lb cold press watercolor paper and at least 3 or 4 paint colors. The trick here is to get the paper really wet - you can paint it with plain water and a brush, you can run it under the faucet or soak it in a tub of water. You want to saturate the fibers of the paper so that they open up and get ready to move the paint.
Put your wet paper on a flat table (you may have to secure the edges with masking tape). Load your brush with paint and add it to a corner of the paper - slowly move the paint towards the center of the paper without letting the brush leave the paper. Once the color has faded from the brush, pull the brush back to the corner (keeping the brush on the paper) and then lift. Rinse your brush well, dip into the next color and begin adding it next to your original color, starting at the edges of the paper.
The idea is to add one color at a time around the edge of the paper, working towards the center. Every time a color is added, make sure the colors overlap, so that the colors blend. If the paper becomes dry, then rinse the brush and add plain water to the uncolored areas.
How big an area to paint at a time is up to you - if you are only using 3 colors, then you'll fill in large areas on the paper. If you're using 12 colors (go for it!) then your areas will be smaller, so that you can fit all of them in around the paper.
The wet paper will continue to blend the colors together after they are applied - but if they aren't blending as well as you would hope then try this. Rinse your brush and dry it really well with a paper towel. Rub the border where one color meets another in a swirling motion - going from one end of the border to the other. Rinse the brush, dry it well and repeat the swirling motion again. Repeat until the colors have softened and blended.
The main mistake that you can make here is not using enough water - so don't be skimpy with the water and load on the paint! After I made my paper I stamped it with the Bird Collage (E1102) in Brilliance Graphite Black ink - and added a red rhinestone for a little extra sparkle. It's layered on a piece of patterned paper from the 6x6 Gingercake collection.