Reworked pattern for worsted weight in 2 colours with a ribbed band. My mods:

MC: main color
CC: contrasting color
Needles: US #6 (4mm) & US #4 (3.5mm)
Yarn: Worsted weight

With smaller needles & MC
CO 80 (fits a 19-23” head)
Join to knit in the round
K1P1 for 2 inches (ribbed band)

Hat section:
Round 1: K 1 round
Round 2: switch to larger needles (K9 Kf/b)
Round 3-7: purl these 5 rounds
Round 8-10: Switch to CC Knit these 3 rounds
Round 11: Switch to MC Knit around
Repeat rounds 3-11 five more times (or until desired length) ending with round 7

Decreases:
Round 12: With CC (k1, K2tog) around
Round 13: Knit
Round 14: (k1, K2tog) around
Round 15: With MC Knit
Round 16: (p1, p2tog) around
Round 17: Purl
Round 18: (p1, p2tog) around
Round 19: Purl
Round 18: (p2tog) around
Break yarn & thread through remaining stitches, pull tight, fasten off. Weave in ends.

Notes: When changing colure, I just carried the yarn up without cutting. This way I had less ends to weave in at the end. If you want the hat to be reversible, then you can cut the yarn, leaving a long tail at each colour change & weave in all the ends when finished knitting.