How to dye rainbows (you only need yellow, blue and pink). 1. Dip one side into yellow dye. Hang to dry, yellow side up. 2. Dip other side into light blue, overlapping yellow slightly to make green stripe. Hang to dry, blue corner up. 3. Dip part of the blue side into pink dye, overlapping slightly to make purple stripe. Allow to dry, yellow side up.