The Harper Beanie uses color changing techniques or basic fair isle. I’ve included a link to a simple tutorial for this.
Extra yarn is needed for the contrast colors and for the Pom.

Sizes include
Newborn
0-3 month
3-6 months
6-12 months
1-2 years
2-4 years
5-12 years
Teen
Adult

Main stitches used for this pattern are back loop only single crochet and basic single crochet.

You can use DK/8ply or Aran/10ply weight yarn for the contrast color. Main color must be 10 ply.
Bulkier yarn is better for a fluffier pom but any weight will do!