Once a year since high school, I've found a single hair that is only partially white (on the bottom or in the middle) and black near the root. It's pretty fun to look at, but I have not real idea why. I think part of it has to do with stress. I think the white happened during the school year, and once the school year ended, the white hair went back to it's original color. I don't put any kind of chemicals in my hair, so I think stress is a huge factor.
