Pumping Discoloration.

I m Asian. Wit fair skin.. I got good result after just 2 week of air pumping. My dick look slightly fatter.
My dick skin color darkens when I pump.. I pump, 3+ hg ,around 6-7min per set. 2 to 3sets.
I using hot towel warm up, firegoat roll and jelq in between. I even apply tretinoin cream .but, the dick still darken.

1. Pump discoloration? Suggestion?
2. Difficult to remain full erection during,pumping. I m watching porn to remain tht. Any idea?(however,I tend to ejaculate afterwards)

Try cold water after you warm down. I have been running ice cold water through bet my package after workouts. I think this is good for the capillaries.