Feel free to change the style of sock when you knit this up. The important bit is the ribbon chart. Enjoy!

The ribbon is added afterward in duplicate stitch, but feel free to do it in fair isle if you please. :D

Errata: When working the afterthought heel, pattern has you decrease every other row until 32 stitches remain. You should then decrease every row until 16 stitches remain before grafting.