I worked this cowl using an old 5g advent I had enough to do both the hat and the cowl. I used the full 24 x 5g colours and one solid main colour to set them off but it would work just as well in a solid colour or in two colours.
It’s named after me as a child, (my nickname) I thought it was right as I love rainbows and have since I was a child.
If you wanted to make this wider on the neck you can always do another full repeat or you could increase the purl stitches between each repeat.