From the Knit Picks Website:
As written this scarf is a very advanced double-knit pattern. Materials requirements are very close so one extra skein for each color should be held in reserve in case you run out of yarn using the initial requirement. For an easier knit you can knit it as a tube, but materials requirements will be entirely up to you and larger needles are required to fit gauge.

Needles:
Size 2 (2.75mm) straight or circular
Size 3 (3.25mm): one needle for bind off