Tux or dark suit and long maxi or floor length dresses or an elegant pantsuit. For the tux or suit, any dark color is great, including black. This is a winter wedding, so for dresses think solid greens, browns, mauve, blues, or pretty much anything EXCEPT white (or anything close to it) and black. The bridesmaids will be in black, please choose another color!

https://www.theknot.com/content/what-to-wear-formal-black-tie-optional-black-tie-invited