Black Tie Preferred?

For me that would mean a dress, no sun dresses. I think a mid-length dress would be fine, and a floor length formal would be as well. No flip flops

As for colors just no white

I would wear a elegant floor-length gown. No white and people tend to stay away from red and black at weddings. I think with black tie you could get away with red and black though.

We went to a wedding that was "Black Tie Preferred" a year and a half ago. FH wore his best black suit and I wore a tea length yellow dress. The only color I would stay away from is white.

I think a dress that is to your knees or longer is appropriate. It doesn't have to be floor length if you ask me. Who is ever going to wear floor length again. Just dress classy, I also think a darker colour is more appropriate.

I have not sent out my wedding invitations yet, but it is going to be black tie optional. Many people have already asked me if it is OK to wear a long dress, and of course I said yes. I expect many people will wear short dresses too, but not sun dresses.

Here you go.

http://www.emilypost.com/social-life/formal-dinners-and-parties/860-dressing-for-the-occasion