Black tie event

To be black tie is fancy. Floor length gown, with/without a small train, colours like black, navy, emerald, or something lighter but sparkly, or even feathery.

Very formal but not white tie formal.

@Alexandra could I wear red or will I stand out?

I'd wear a floor-length dress with heels or sandals/flats and my diamond earrings, a necklace, maybe, and a bracelet, maybe.