How we did it:
- masking tape
We grabbed some crayons and masking tape and taped a few together in the order that my kids requested.
They must be taped evenly so that all will touch the paper at the same time.
My daughter (5) thought this was the perfect rainbow-making tool. My son (2) insisted this was the wrong way to color and had me remove the tape from his set. Haha! Can't please everyone, I guess.