From pattern introduction:
Sized for Mom, Dad and the kids, these boots will keep the whole family warm. Knitted in a tweed-effect wool yarn on two needles, the Fair Isle effect is created by slipping stitches and is continued across the sole. After knitting, the socks are felted to create a beautiful blurring of the colours and then finished with zippers.

Pattern is for 5 colours of yarn; yardage above is for the yarn you need to buy, depending on size there might be quite a bit left over.