At my college, there were two events (one in the early fall and one in the summer) that required white dresses. You were informed about it when you received your information packet following your acceptance, so you had plenty of time to find one. (It was a tradition that had been going on for more than 100 years.) So many people started to complain about finding a white dress, that they decided to use it as an excuse to get rid of one of the traditions and they said any color dress would do for the other event. I'm still bitter..