The origin of these socks is at the center of the diamond at the instep. Then you work a Judy’s Magic Cast-On down the length of the leg and foot, working it around the diamond. The sides of the sock are worked back and forth simultaneously, so when a gradient yarn is used, the pattern is mirrored across both sides.
Instructions are given for a five-shade gradient kit, which gives you control over where the color changes take place. You could also use a single skein of gradient-dyed yarn, if you like to let the color changes fall where they will. Second picture shows a pair made with variegated and semisolid.