Women can get away with a nice dress as long as its not a summery print like floral or something. Something black always works well with a nice pair of gold/silver shoes if you have them. It adds a nice contrast to the black dress.

Mens suits can be black, grey or navy and with a shirt and must wear a tie.

Black tie is bascally no open collars, denim, beige pants or sport coats ect. Men have to wear a tie and dress shoes.