What can I do for premature greying?

Satvic lifestyle definitely stops pre maturing greying from advancing. It would to some extent work in reversing it as well. Along with the complete Satvic lifestyle, you can also do the following:

Cut an amla (Indian gooseberry) into 4 pieces and soak them in a small bowl of cold pressed coconut oil. Cover it with a muslin cloth and leave it in the sun for 15 days. Strain the oil and massage into the scalp. Next morning, wash out with home made shampoo using Amla, Shikakai and Ritha. Soak the powders of these ingredients overnight. Mix them in equal proportions and rinse out the hair.