Want to make your own?
Card board (for inside the shirt)
Tulip Slick dimensional fabric paint black & white
Tulip Color Change fabric paint: red, blue, green (other colors available)
stencil (or freehand your design onto the shirt)
Step 1: Place your stencil on your shirt and outline it with the black Tulip paint. Allow to dry.
Step 2: Fill in black outline with white paint. You may need 2-3 coats. Allow to dry.
Step 4: Out line design with white paint. Allow to dry overnight.
Step 5: Head outside into the sun and watch you white design "magically" turn to color.
Also I've decided to join in on this: