I'm in the process of going grey.. or rather I am in the process of having stopped colouring my hair and am waiting to find out what I really have 
I am 47 next week and this year suddenly noticed that the few scattered unnoticible grey hairs have suddenly bandied together to become little streaks , mostly under my fringe and round the front. (mid brown hair) I also noticed that despite a good colourist I have rarely been totally happy with my hair, either a tad too dark, or too light, highlights too thick, too fine.. yadda yadda so I decided to stop..I'm now 6 months in.
I now have brown hair with a white streak at the parting and many scattered white hairs elsewhere..and they shimmer in the light, look fabulously healthy and I can't wait for them to be long enough to be my hair all over. True, currently the 3 inches of white root and darker ends isn't pretty, but I don't look dreadful (it's not even very obvious unless my hair is clipped back for sports) and the light colour frames my face better than the brown did.
I figure if I grow it all out and hate it.. well then I will have a fresh head of hair to highlight or whatever, but if I can manage 18m of growing it out, I will have chemically free healthy hair and I don't need to look 'young' . I'm the mother of 4 adults, I'm slim and fairly fit and I am going to rock the white streaks look if I possibly can!
Dh is pretty bald with an almost white short beard, and says he is just jealous mine grows and he really doesn't mind what colour it is!
I work in school, and my decision was partly prompted by looking at all the middle aged ladies with dyed heads (you can tell staff meetings are riveting
) and those few with natural hair, and thinking that they looked better. There were so many ' roots showing 3 weeks in' heads, so many 'beige blondes' and only one lady with truly beautiful hair.. whose daughter is a colourist!
I'd rather be individual!