[mlok]

I have long dark hair. I can notice this myself. Some of my hairs are dark at the tip, then turn white, then turn dark again nearing the root. That surprised me the first time !

And yes I can count them : easy to spot the white loners in the dark crowd. (You don't need to mark them : they are their own timeline history, if you do not cut them)

Empirically I more or less came to the same conclusions than this study 5 years ago.