According to the official website:
National Wear Red Day—February 1, 2008— is a day when Americans nationwide will wear red to show their support for women's heart disease awareness. This observance promotes the Red Dress symbol and provides an opportunity for everyone to unite in this life-saving awareness movement by showing off a favorite red dress, shirt, or tie, or Red Dress Pin.
What a fantastic cause, and something we all need to be genuinely concerned with. It's not given enough attention, and often looked over for some of the more prominent, and less advertised than for instance AIDS. Not to implicate that it is not as important, but the media needs to make it that much more important. So stay aware of your blood pressure readings, visit the doctor often and live healthy.