Wet the shirt just a bit. You want it to be damp but not soaking wet.
Cover your work surface with a plastic table cloth you can throw away when finished.
Lay the shirt down on a flat surface. Grab a piece of the shirt in the middle and start twisting.
Wrap 4 rubber bands around the shirt holding it in place. Tuck in the loose edges when possible. You should have 8 triangles when finished.
Mix the red and blue dye according to package directions.
Place the shirt on a wire rack and alternate the red and blue colors. If you want more white space, only color every other triangle. If you want more colors, squirt dye on each triangle. Don’t add too much dye to where it is dripping constantly onto the surface below.
Flip the shirt over and add dye to that side.
Place the shirt in a plastic bag and let sit for 8-10 hours.
Cut off the rubber bands and rinse the shirt under cold water.
Wash separately the first couple of times to get rid of extra dye still in the shirt.