I found one this morning, hiding among all of my brown hairs. It was silvery, almost pure white. I’m only 20, why do I have a grey hair!?! :mad:
Two relevant articles from Cecil:
I find it interesting that there seem to be no studies examining stress as a killer of melanocytes. It certainly does wreak havok on other organs.
My father, and all of his siblings, have prematurely gray hair. Their hair went completely gray while they were in their 20s. It appears to be a recessive gene since none of their children have prematurely gray hair.
About fourteen years ago, the “sideburn sections” of my beard appeared to turn white over a period of about two weeks. The entire beard had been “salt ‘n’ pepper” (light on the salt then) but the sides, the areas over my jaw muscles, became completely white seemingly “overnight.”
This event coincided precisely with the cataclysmic meltdown of my marriage. (I have been married and divorced three times; when I characterize this one as “cataclysmic,” I know whereof I speak.)
Now maybe my chops were due for a whitening anyhow; I dunno. Today my beard is about 90% white, and the rest of my hair (on my head, that is) is gradually abandoning its formerly nearly-black splendor in favor of colorlessness. I become more “distinguished” by the month. 
But that sudden change – upon which a number of friends commented at the time – and its concurrence with my second marriage calamity… Well, it makes for good conversation at the local pub.