Apparently most grey hair is caused by a build-up of hydrogen peroxide in the inside of the hair. Neither of the articles below say just how or why hydrogen peroxide builds up, but if there is a cure I am sure most grey haired people will be happy. And that the cure is available soon.
HP is also apparently the reason for vitiligo from which Michael Jackson suffered, though in his case I suspect that the hydrogen peroxide (or whatever was the cause) was applied with his approval.
I have seen a few people with vitiligo and it does not look pretty with pink or pale skin dappled with much darker skin. I guess white people could suffer from it too, but no one would notice it much.
Gray hair and vitiligo reversed at the root
Grey Hair Treatment Discovered By Scientists
Sorry, haven't found any references to this research in The Lancet, New Scientist etc. so this all may be speculative. I hope it isn't.