59 here, started going gray more heavily after DH passed away last year. My sister wants me to color it, she is more gray than me but uses a men's color treatment to make it less gray. I don't mind being gray. I keep thinking of two women I knew. One was in her 80's and still had jet black hair. Looked like a fake fur coat. The other was my SIL, she went through heck when she finally decided at age 60 or so to stop coloring her dark brown hair. Finally settled on a light blonde.
I wouldn't know when to stop if I colored my hair - 60? 70? 80? at some point people stop thinking how nice you look and start thinking, who does she think she is fooling?
Besides I earned every one of these gray hairs.