I'm going to say what everyone else has been saying. It goes by individual chapters. The funny thing is that our chapter used to have a nylon-wearing, closed toed shoes only rule also. But I went to Convention 2 years ago and saw everyone else in open toed shoes without stockings... Whoa, the amendment to the chapter constitution was written before I got on the plane to go home!!
We mainly dress like you would on an interview or in a business. Nice skirts and blouses and if you wear pants, you must wear a third piece as well.