Hello Samuel,
Thank you for posting on HCM.
Greying of hair occurs when the 
melanin of a particular hair follicle is permanently exhausted.Premature greying of hair is attributed to many factors like diet,nutrition, UV rays, pollution, cosmetics/dyes/colors, genetics, medications etc.
Treatment of grey hair is pretty challenging. I would advise you 
biotin and 
calcium pantothenate combination tablets for atleast 6-8 months. Apply Altris gel containing Melitane, which is a new compound shown good results in premature greying of hair. Also, a novel hair sunscreen cum hair serum Q sera black has shown good results in prevention of hair damage from sun and pollution.
Take plenty of fresh fruits and vegetables in your diet and try to de-
stress your lifestyle. Try to limit your 
smoking and alcohol intake. 
I am sure this will take care of your issue.     
Thank you
Dr Hardik Pitroda