I did this for my newspaper class, February issue. Sadly, it didn't print in color, so I wanted to post this, because I can.
1
Start out with a piece of clothing which is light-colored. Try white or beige. Avoid blues or greens.
2
Start out with your first color and begin to tint your look.
Use my spray paint tutorial to make the right colors.
Mix your two main colors first.
3
Next, mix your second color with your first one in a third spray bottle.
Mine came out a lovely lavendar.
I sprayed it around the edges so that it looked like the blue was blending into the red.