There seems to be a lot about immune system activation attacking melanocytes like this: https://www.uab.edu/news/research/item/9390-study-explains-one-reason-h

There seems to be a lot about immune system activation attacking melanocytes like this: https://www.uab.edu/news/research/item/9390-study-explains-one-reason-hair-can-turn-gray#:~:text=Hair's%20graying%20is%20linked%20to,can%20decrease%20pigmentation%20in%20hair https://www.uab.edu/news/research/item/9390-study-explains-o.... Thus not surprisingly “Covid and gray hair” brings some results too, including reversing of Covid associated gray hair.