I have been struggling with the outward beauty/inward beauty thing.
My ex-wife was -- and still is, at 38 -- gorgeous. But I have finally realized that her beauty warped her personality. In junior high she was the envy of all the good looking and athletic guys, and I was a romantically backwards nerd. I think -- and women I have discussed this frankly with have confirmed the general phenomenon -- that she could be more rude and self-centered in a relationship because the guy of the moment could be (and was) replaced by the next guy in line. So in general I think there are very few exceptions to the "pretty = b*tchy [1], plain = nicer" rule of thumb.
I have deliberately reviewed my list of "if there is a next time" spouse criteria and moved all of the physical/outward attributes down in the list. But I still find, as a guy, my eyes turned and heart rate quickened by the pretty ladies I see in my daily life. Even as my brain is saying, "remember, hot equals trouble", I find myself having to remind myself to look past the looks and get to know the person.
I had been watching "Age of Love" (the show where a 30 year old guy is dating a group of 40 year old women and 20 year old women) and realized that I must be getting older, because although most of the 20 year olds were hot physically, their brains just didn't even seem to be there, and their personalities were very minimal, and their kindness towards others and awareness of the rest of the world were non-existent. I found myself rooting for the 40 year old crowd.
As for hair, I think women with black or dishwater blonde hair can pull off the graying look. Brunettes or redheads would probably have a harder time.
Me personally? I have dark brown (my 7 year old son claims it's black) hair and am overall maybe 1% gray, but I keep it extremely short (#2 clipper) so I think it looks OK. From a female point of view I bet my extra 25 pounds would probably be more of an issue.
I also think that there are different things that specific individuals find attractive or unattractive. Gray hair in a lady wouldn't bother me much. I find I am attracted to women who have strong facial features and have their hair pulled back. I've no idea why, that's just what I like. So, for example, I think Jane Goodall was an attractive lady in her day.
2Cor521
[1] Pardon the French.