I haven't been working on my Monkey socks too much recently, but I did manage to turn the heel:
I like the way one side of the heel is mostly blue, and the other side is mostly red.
I'm using Lang reinforcement thread in a dark blue color on the heels.
Out of curiousity I looked at the sock through a pair of red-blue 3d glasses. It caused the colors to flicker a little, but that was about it.