I have had grey hairs since I was in my late teens - it's a thing in my Dad's family.
I have lovely thick dark hair. I am very happy to let the grey show most of the time - at one stage when I had an older lady to manage who really didn't want a "young girl" managing her (and felt, totally wrongly!, that she'd been passed over for a much-deserved promotion! (as she had seniority but was actually really not that good at her job)), it was really useful to show the grey as a sign of not being about 20 at the time (I was quite a few years more, but she used to treat me like I was a teenager).
I have got temporary colour put in for a few family weddings in recent years - as eldest, I had a long gap between my wedding and some siblings weddings and had a few periods of serious stress adding to the grey before then.
I also have a habit of getting "candy cane stripes" of red highlights put in for Christmas (I am a Christmas lover, and also as a respectable senior civil servant, it's a time when such frivolities can be allowed 
!!). But they fade out quickly enough most years (this year, we went for bleaching out the stripes first for getting good impact on the red - so the dirty blonde parts had to get a temporary brown over them for a while but even those have now grown out again).
It's only hair.
I am still young at heart, and have often had people asking me if my parents were at home if I answer the door not in work clothes (I am living away from them longer than I lived at home at this stage!). I keep my skin well, I have a good cut to suit me, I do wear makeup....but I like the look of the grey and I don't necessarily think it is ageing, actually. Instead, I like having the confidence that I can wear my hair as I want to. And not have to conform to society's expectations of me as a woman - I am a person in my own right and can make my own decisions about things like hair colour, body hair removal, levels of makeup, etc - to suit me and my personality.
I am NOT Spartacus!