Pumping and Testicle Damage?

I just started using my Penomet and everytime I pump for 10mn straight, my ball sack is slightly discolored for a short while after and my balls seem to be smaller and hanging for at least a few hours afterwards. I don’t know if this is normal or something I should worry about. I really don’t want to damage my balls from lack of oxygen.
I know theres a lot of people who pump, so any help would be appreciated!

I did end up taking two days off and my scrotum felt slightly sore the day after pumping but everything seems normal now.