Hii doctor I am 16 years old and my hair starts greying 2 years ago so to prevent my hair greying I used patanjali kesh kanti hair oil but it doesn't work then I use amla hair oil but it also doesn't work and I also used many home remedy but all are wasted then lastly I started colouring my hair with heena but it removed from my hair in 15 to 20 days I am very worried about my grey hair so plzz tell me what can I do to black my hair.