Some coolness is normal with hanging as well as some color change. I think the manual needs to be re-written in this area. I have asked BIB about these same issues and he always says it is nothing, even though the manual says no. I read almost every post at on hanging and read that you should stop hanging if the head turns white (along with the coolness),yet, when i asked BIB in a pm about this he said it was normal and that he got that nearly everytime he hung. This is a touchy area and for now ALL I can tell ya is to make sure that between sets that you jelq lightly to restore circulation.:banghead:
Yes, a little cold is ok. Ice cold is bad. As long as it's not black, ice cold, or NUMB, or feeling like it's "falling asleep"...you should be ok. Also, make sure you are hanging with a weight that is giving you a good fatigued feeling by the time you finish your sets for that day, but at the same time not so heavy that you can barely hang with it for long and causing negative side effects.