I think it's unfortunate that the blogger Tarzy linked did an apples/oranges comparison since it basically blows the whole compare and contrast thing out of the water.
I weighed in on a recent grey hair thread with this link:
http://goinggraylookinggreat.com/
because I think the vast majority of the women DO look great, and frequently much better than they did with artificial color.
[But then I think many non-greying women who color their hair -- at home or professionally -- end up by choice or accident with non-flattering shades.]
Frankly, 40+ is when a lot of past and current bad habits catch up with people. Sure, we lose our naturally dewy skin texture to some degree as we age -- but sun exposure, smoking, crappy diets can all make the skin look very non-youthful as all impair circulation and cell renewal.
It's been said by others more eloquently at various times, but I think a woman with grey hair who takes care of her health as best she can and eschews drab colors, don't-mind-me clothing, and a random haircut will often look much more VITAL and yes, often more youthful than women who make other choices...but dye their hair.
[FTR, I'm not ready to transition yet (41, greying since 16, get pro color every 4 weeks but need it at 3) but do see it happening once I get to a certain point of non-patchiness. My re-growth is 1.5 inches a month and it's tedious and spendy to outwit it!]