This is a subject that has been discussed here 100s of times before.
Perhaps these Longecity site search links will give you some ideas:
https://www.google.c...ey hair greying
Increasing Catalase to neutralise H2O2 is probably your best bet. Cocoa, resveratrol, vit E (all 8 forms) etc.
As telomerase is active in stem cells, germ cells and hair follicles; looking at a telomerase activation stack, starting with Epitalon may be a good idea.
C60oo is extremely good at neutralising ROS and seems to synergise with telomerase activators.
Use the site search demonstrated in the link to find out more from posts here.