I found my first grey in my mid-twenties (a decade+ ago) but I've been going more and more grey since my early 30s. I'm 38 now and I have a fair amount of it. I don't cover it up and I have been told I was "brave" for keeping it grey. I think a lot of women start to cover it up and then end up feeling trapped by the constant upkeep. That's just my thought, though. You should definitely do what feels right.