I am usually the first one on the "sexism" bandwagon, but not in this case. The only reason it is news is because women are traditionally more vain than men and, therefore, do much more than men to improve their looks....with clothes, with makeup, with jewelry, with hair color. I would bet if they didn't....they wouldn't be noticed the way they are.
It is also news because Demi Moore has always had noticeably long and beautiful brown hair, so if someone decides to make mention of her more "laid back look" by pointing out the gray streaks, I don't see it as a big deal. In fact, in the same article, mention is made of how great she looks. I disagree with your outrage in this case.