My beard was first by at least 5 years. In the intervening years until today, all of my beard and head have greyed except for a patch on the very back of my head, including my nose hairs. Oddly enough, the only exceptions have been my eyelashes and body hair where I maintain my brown color.
Head by far. I had a few gray strands going by my late 20s, and now at 41 I’m still predominantly black but obviously peppered with gray.
Meanwhile I have exactly two white beard hairs, and all my body hair is still solid dark.
This is probably unrelated but I’ve found that females and unbearded men are always surprised to find out that beards shed like crazy. Think about how often you find a piece of hair on your desk or table or your clothes (on in your mouth or food)…I find beard hairs all the time, like at least once or twice a day. When I first grew my beard I used to play with it and would find them constantly. Enough that it got kinda gross and I actually stopped putzing with my facial hair just so I’d stop finding it everywhere.
So, I have no idea if beard hear going grey is related, but it does ‘shed’ much faster/more often then head hair.
Facial hair went grey first, so I went “clean shaven”. My wife was pretty upset because evidently she really loved my moustache. I’ve toyed with growing it back, along with a full beard but employers seem to hate facial hair.