Too embarrassed to go to doctor so I'll try this.
I have had this kind of marks since I was a kid and they keep appearing and dissapearing on my penis from time to time. This one on ym shaft however is always there and looked more like a scar and was almost invisible but it recently changed color to this (it is hard to see on this photo but it is more of a purple color). It does not hurt/itch or anything. I'm not sexually active (probably becuase I'm embarrassed to show it to anyone...).