This is the story of a friend who has been with me since 8th grade , his hairs started greying while we were in 10th grade together , he didn't usually care about it and accepted them he says , but all changed when he joined a gym and took supplements along with a high protein diet (Biotin, fishoil , multivitamins , FOR ATLEAST 1-2 YEARS HE SAID) during this tenure he didn't use any kinds of dyes . He is now a fitness coach in mumbai and has reversed his hairs to atleast a 98% of reversal with still has only a single grey strand left rn . Im posting this as my little brother also is facing the same issue and spents alot of time on this sub. (note - he lives in Navi mumbai , India ) He also said a important point that is people who grey at the age of 15-20 have a very high chance of reversal ofc only if nutritional deficiencies (genetics almost very low)
He sometimes takes ashwagandha for lowering his cortisol for good sleep.
And trust me his hair are 100% natural in colour if he would had dyed it , would have been extremely obvious. yes it is natural
If you want I can ask him more about his story