The pattern is for a Jolly Girl Hat for 2-5-year-old girls.
You need a 3.5 mm crochet hook to make the hat.

If you wish to make it larger, use a size bigger hook, or if you need a smaller size, change to hook 2.5 mm.

I used sport weight cotton yarn, 6 colors altogether.
Catania, Gilice, or Alize Bahar and Bella would be perfect choices. It also looks great if you use only one color, the texture will make it look very interesting.

If you have leftover yarn, this would be the perfect project to use it up.