Guage isn’t important in this - I held the sport-weight Cascade 220 double for the black bits and had a thick, slightly felted single for the brightly colored bits. Any worsted or bulky yarn would do great for this and there are instructions in the pattern for making it bigger or smaller.

(Note: this is based on this Stained Glass Cowl. I modified it go around your neck only once, added buttonholes, and changed it to knitting flat instead of in the round, along with a few other modifications. Many thanks to Tenthfloorskybox, aka Leslie Gersing for her inspiration!)