Basically you just ink up a solid stamp with one colour of ink (Wild Wasabi):
Then you stamp on it with another stamp in a different colour (Garden Green):
Do that all over your stamp and then huff on the stamp (to re-moisten the ink) and stamp on paper to get something like this:
Here is the card I made:
The tiny flower is from Mikes's Busy-bee stamp set and I also used Mike's Gecko. The vine down below is a die cut that I accidently glued onto the bottom of the card rather than the side (like I wanted) but I actually think it looks better there so that must have been fate or destiny playing a part there...or maybe just me rationalizing the whole situation. The paper for both the card and the vine is Garden Green.
The finished card is 5.25x5.25.