Some people don't wear black to weddings, but again these days I think at every wedding I have been to someone was wearing black. The other one is white or cream! I would steer clear of anything that looks too "bridal" but other than that go for your life!!
The last wedding I went to I wore a bright pink and orange (with other colours!) maxi dress, that went to the floor and I loved it! It was flowy and bright and made me feel happy just wearing it which is great on such a happy day!
Good luck hun!