I don't know. I don't think that there is a "dress-code" or style for trance parties, or clubs. I guess I wear whatever seems to catch my eye on any given day. I tend to dress casually with a little flavor. But then again, I don't know, I've seen so many DJ's that would dress totally randomly, and vary from one to another.
There are Dresscode's at certain parties, like Sensation White, you have to be in White, Sensation Black, you have to dress up in black. Qrime Time, you have to be dressed up like a gangster.
But Trance itself hasn't a dress code. When we had the Hardcore periode ('92 - '99) you had a certain way to dress, Bald head, Australian or Cavello training suite, nike air max shoes. The trance scence doesn't have that.
The thing that there isn't a dresscode (like in hardcore-periode) makes trance beautiful, Everyone can listen to it, without being a (stupid)-follower, like those wannabe gangsta's or wannabe hardcore 'nd stuff. Get your own life -> listen to your own style