Ursula

You definitely don't want brown with that, I think, at least not a mediumish brown; a cooler color that plays off of the skirt is a much better idea; black would be a good default, and it's certainly the safe choice. You don't have to wear heels with it, but it's a somewhat hard length; I think anything other than sandles or (slim, at least mid-calf) boots might be a mistake, but that'd depend a little bit on the details. Basically, with the height that the hemline is at, you don't want anything to visually split up that space further, so you need something that either doesn't read as taking up any of it (sandles, preferably something relatively non-bulky), or something that smoothly takes up all of it (boots). With boots, heels might work, although you can definitely do it without them. If the wedding isn't for a little while yet I'd go with boots; I think that's the better of the two looks; OTOH, they'd be a bit odd at a summer wedding.