I've had a lot of thoughts about this.
I have thought that coloured hair on women is a bit like coloured bathroom suites (bear with me hear... I am going somewhere with this...!).
So sometime in the early-mid 20th century, it became possible not only for most/all women to permanently dye their hair, but also for most people to acquire coloured bathroom suites.
We then as a society got very very used to seeing both coloured bathroom suites and dyed hair on women - both of which were a novelty on the whole to society, and a marketing success.
Over time we have got tired of the coloured bathroom suites. Apart from fairly niche suppliers now, the days of avocado or champagne porcelain in every bathroom are over. It can easily look grubby and tired, and it's difficult to maintain if one thing breaks. I think that in the whole of history, coloured bathroom suites will be seen as a novel blip.
Same with women with coloured hair. Obviously there will always be women that will. But it will, I am sure, also become less of the norm, as women just get fed up with roots, and orange/green hues, and putting harsh chemicals on their skin.
I can't believe the PPs who say that grey hair can be a 'stripy, patchy mess'. Maybe if you are comparing it to the adjacent colour at the growing out stage, but stripes are actually natural highlights are they not?
I can't wait until a time where women, whatever their complexion, focus on healthy and easy-to-maintain hair and skin. Nothing looks better on a woman IMO in terms of hair/appearance, than a good hair style, healthy glowing skin, and most of all a smile that reaches the eyes.