You will need:

• One solid color (cream used here)
• A multi-color yarn
• 8 colors of Koigu were used here, 10 rows of each.

Some of the Koigu colors are no longer available, so I recommend buying colors you like and laying them out in order of the rainbow and do 10 rows (or to your liking) of each color between cream colored yarn rows OR use a self-striping yarn instead.