From Knitty:
This sweet little sock is a tribute to the idea that something rather simple can look truly beautiful, and be functional as well.

Since Simply Socks Yarn Company opened its showroom in August of last year, I’ve been spreading my sock-knitting and color-loving wings, partly due to the dazzling panoply of color I encounter when I stand in front of the display of their custom-dyed solid sock yarns.

I’ve been a self-described Color Fearist (instead of theorist), but something about combining colors into one-round stripes has unlocked several possibilities for me. I chose these two colors, Chocolate and Tangerine, because they reminded me of one of my favorite forms of chewy chocolate - Tootsie Rolls.

The two colors of Simply Socks Yarn Company’s Simply Sock yarn wind around this sock, switching on every round. A column of purl stitches eliminates the need for any concerns about color jogs. The stitch pattern, in effect, hides the changes from round to round. The twisted stitches lift up parts of the fabric as well, making the colors ripple together, like marble or swirls of fudge.

The afterthought sock heel uses a toe-up gusset construction as a starting point and very closely imitates the form and function of a traditional flap-and-gusset heel. There are no picked-up stitches, except for what is picked up from waste yarn, and since the heel stitches are independent of the rest of the foot, the entire thing can be removed and replaced, if needed. The cast off, described by TECHknitter as the “stretchiest bind off,” curls over the top of the sock. I overachieved a little on the leg of my sample sock (size medium). I think, if you made the leg 6 inches long instead of 7 inches, you could get a pair from just 2 skeins of yarn. Otherwise, you may have a lot of leftover yarn. Speaking of which, the careful, or freewheeling, knitter could use this pattern for leftovers. It would be a lot of ends to darn it, but I think it would be perfectly lovely to see stacks and stacks of different stripes throughout the sock.

I also have a photo tutorial with more details on working the heel here.