what causes discoloration?

I have some discoloration at the top of my glans, it’s from one hanging session I did OTS. I am thinking it was caused because there was too much pressure on the glans or too much blood in the glans while I was hanging? But the thing is that is the only way I can effectively hang OTS because the skin stretches almost over my glans (and I am cut) and there is almost no grip on the inner penis, the only way I can get a good stretch is when the blood in the glans is applying stretching pressure. But I don’t want any more discoloration.. so what else can I do to prevent my skin from stretching over the glans?