I have plenty of leftovers from the Zzzap shawl I just finished, this is Zauberball from Schoppel. It's a self-striping sock yarn with slow colour variations, and doesn't repeat the same colours. This yarn is similar to Knitpicks Chroma, Regia Hand-Dye Effect, or, for non-nylon fingering weight yarns, Jojoland Melody or Kauni Effekt.
I really, really love this yarn. It's not cheap at all, but knits up wonderfully if you like wild socks. Your two socks will not be the same, that is guaranteed!! If you want your socks to be identical, this is not the type of yarn for you; at least, not for socks. The repeats of the colours are too unpredictable to get symmetry to happen.
Here's a pair of (non-matching) socks I just finished for my youngest son (14). He's rather adventurous when it comes to socks!