From book’s pattern description:
You can’t go wrong using color combinations that exist naturally. The rainbow is an example of this. My version is a little bit brighter than the rainbow in the sky, but the colors look beautiful. This hat is terrific for baby boys or girls, and a perfect alternative to the pale yellow I-don’t-know gift that everyone receives before a baby is born. You’ll be the hit of the baby shower when you show up with this hat for the mother-to-be.
Link to video tutorial for topper: