There's a product called Regain (so its called in Europe- dont know about USA) - tablets which make your hair grow back in your natural colour.
As an in-between solution just use colour toner - but after a while you'll find that there are no more grey roots, and at some point you can stop using the toner.
A natural way to cover up some few silver hair far apart is HENNA hair-die- if you have too much grey, however - it will not help really.
Advantage of Henna is - it leaves your hair nice and shiny and never damages hair, unlike bleach (peroxide=contained in most hair bleaches) and real die. Colour toner is also more gentle to hair.
It's a question of character as to WHEN you want to grow your grey hair out and carry it with pride.
If you are past 60 - I give you a tip: make close-up photos of yourself and others within a group of people several times a year - and look over them every now and then.
When you find you have too many wrinkles for your jet-black hair - switch to your natural grey - and you will actully look BETTER - if not younger - but less ridiculous like that Ronald Regan who died his hair jet black with 75+ while his wife sported her silver locks!!!
To be good looking, colour of your hair is not as important as the fullness of your mob - AND good styling.
There's another way to keep greying at bay: healthy diet= 5 portions of fresh fruits and veggies a day - sports and fresh air.
At the end of the day: genetics have a lot to do with when you start turning grey- just watch your (grand-) parents and photos of them, and you'll see what you can expect. Balding and hair loss - also mostly inherited (genetics) make you look older and less attractive, and this can have some other causes, too (illness, stress, some medication, menopause, some contraceptives).
For men as well as women who are getting thin hair or start balding, here's the answer: http://regrowyourhairnow.us