I think it all depends. I know that in some places you get your bid and you don't go straight to the house. Or you go to the house right away, get a tshirt, then go back later and change for a more formal dinner (that's what they do where my daughters went to school).
When I was a pledge they came to our door with a big sign and told us what time to be at the house and to wear a blue dress if we had one. So pledges wore blue, actives all wore black.
It was years before I could pass by a good deal on a black dress...oh wait, I still can't.
