...so easy, but SERIOUSLY... it took a dozen attempts to get the look I was reaching for!
You can find more information on this technique here: http://www.splitcoaststampers.com/resources/wetpaperwatercoloring.php
How I did it;
I sprayed a peace of water color paper with a water mister to make it slightly damp. Next I inked my background stamp (with dye ink) and sprayed the stamp lightly with the water....stamp/repeat. I let the paper dry then stamped with the outline stamps.
Stamp sets used: Wonderful You, Itty Bitty Backgrounds
Inks: bordering blue, brocade blue, night of navy
paper: night of navy, naturals white and bordering blue cardstock; water color paper