Mystery

My beard and moustache grow in very dark brown, just like my hair. I recently didn't shave for a few days, and a thorough search by my wife revealed exactly one white hair on my chin, but no other grey (it will come soon enough I know).

When I tap my electric razor out in the sink after shaving some of the trimmings that come out of it look grey.

WHY?

I know it's a pointless thing to waste my thoughts on, but it confuses me most mornings...