What an interestingly varied bunch of opinions! As they say, it takes all sorts....

What does it to me is silky straight hair, thick right down to the ends. Anything from shoulder-length on will turn my head, but the real heavy breathing starts around waist-length, and from then on it's the longer the better until it reaches the ankles. Anything longer can't hang free to ripple and swing with the lady's movements.

Not too fussy about colour, though I've always had a soft spot for brunettes.

BTW I think that "ordinary, boring" brown hair is much underrated, often by its owners themselves who insist on dying it to another "more interesting" colour (my daughter, for one). It often has subtle nuances of colour that you don't get with blonde, black or red hair, and certainly never with dyed hair. Ever seen a brown-haired lady step into the sunlight, and the highlights suddenly fire up in her hair? Beautiful!