I'm actually still in college. 4th year.
There are so many times that this happens that I lost count.
Since I have many different classes scattered throughout the days in a set, if somewhat flexible order, I get to see dozens of different girls in a single day.
The first two weeks of a semester, I actually spend scoping out which girl has the hair I most like in each class and start sitting behind her(no forced seating arrangements, you see).
For a time, I sit my chair right behind hers, as close as I can, and subtly pay with the strands of hair I'm lucky to get, all the while getting to know her and making myself her friend.
It eventually gets to the point where I just flat out tell them that they have beautiful hair and that I admire it and politely ask if it would bother them at all if I gently played with it. I gain confidence with one girl, then subtly start moving to another.
Strangely, ever since I started doing this(way back in 9th grade), only two girls have ever told me that they wouldn't enjoy it. Every other girl has been just fine with it and now, I get to play with dozens of girl's hair almost on a daily basis.
Some even sit down and ask me to, actually arguing with me to play with their hair and not another girl's. "You're going to play with MY hair again today, aren't you?"
College really IS the best time of one's life.