The fashion crowd has chimed in and they're certainly not wrong. That said from a practical standpoint, outside of the one-off fashionistas and overzealous folk working the door, very few people will be paying that much attention to your shoes if they're matching your pants.
I am completely wrong if this is a snooty crowd having a wedding at a country club or something extreme like that. For the most part though your average person is enjoying the wedding not inspecting everybody's shoes.
If you want to Google some general guidance, formal is generally somewhere between cocktail and Black tie.