Really. as long as you aren't in jeans, or your jammies, it will be fine.
There will people in black
There will be people in white
There will be people in trousers
There will be people in stuff so odd that you wonder if they've ever been to a wedding before, or even seen a picture of one.
And no-one will really notice or care what anyone else is weasring once theu've had a few drinks.
Really, wear what you like it will be fine