Instead of ribbing for the cuff of a sock, here's a two-colour folded hem.
I cast on and put a marker in the first stitch, then knitting every stitch I worked 16 rounds of the contrast colour, 12 of the main, then I knit each live stitch together with its corresponding edge stitch (the marker comes into its own at this stage). Another time I might use a smaller needle for the first 12 rounds, the better to accommodate the fold.
The wool is a sock set called 'Lobster Pot', bought from Vykky at West Green Loft Yarns some time ago.