Are you getting invited to weddings? Aaron Marino of alpha m. addresses what color belt and shoes should be worn with white plain polo and khaki pants.
If you are going to be in a wedding but the hosts don’t specify the color of shoes / belt, ask them. Also always go with something safe. You don’t want to stick out on somebody else’s day. Opt for brown shoes / belt. You want to more crazy? Go tan.
Also make sure your polo shirt and khaki pants fit you amazingly and that you will wear these items on more than this one occasion. Brown or tan shoes are more versatile than white. Remember, you want to stand-out in a good way and make your purchase versatile.