Maybe beards grey earlier than heads? (*)
The replacement is larger, with a deeper well that doesn't clog so easily, and I confess to not always emptying it after every shave. The other day I looked at the shavings in the trash and wondered why they looked so much greyer than the remaining hair on my head.
Maybe ground-up stuff just looks greyer, because light bounces off more different surfaces? But there are plenty of colorful powders, so that can't be the whole story.
When in doubt, grab the microscope. Unfortunately, colors tend to be washed out and hair is somewhat translucent to boot. But I could easily see that the hair wasn't cut cleanly, and the ragged edges extended farther along the hair than I'd have expected, and a lot was tatters. Hmm. I probably need new shaving heads.
One oddity jumped out at me. Many of the fragments were clearly the same thick size you expect from beard hair, but there were some finer fibers too. What were they? Vellus hair? If so, why so relatively long?
Googling brought up the disconcerting subject of mites and their presence in beard shavings, which brought to mind the thought of spiders to eat them. Hmm. Anything small enough to catch mites won't use webs, so those are probably vellus hairs. Still...
I clean out the well after each shave now.
(*) It apparently does-beard hair grows faster than hair head, and several people suggested that as pigment production slows, the beard hair shows bleaching sooner.