You can use any chunky yarn, but you will want it to have long strands of color before a color change in order to get defined rectangles. Another option is to pick 2 contrasting colors and change colors with each tier.

Pattern contains instructions for a “backwards knit” version of the purl rows as well as instructions for a purl version. The advantage to the backwards knit is that you are not constantly turning your work. For more details on backwards knitting, search “backwards knitting” on you tube.