Welcome to HCM.
I HAVE GONE THRO your detailed description. It is nice to know your exercise duration and pattern, which is so important for health.
The only difference according to you is the jock strap.
This can potentially cause the color change due to the way it fits
the area during exercise.
This does not sound urgent, but whenever there is a next appointment, pls do not forget to take an opinion for your GP.
Wishing you good health