Just wore light blue with a green/blue striped knit to one on Saturday. I figured nobody is picking blue or green for their weddings so I might be safe. I got there and the colors were black and purple. Just like the last several weddings I'd been to. They are so original.
I was also the only guest, besides my girlfriend, not wearing black with a white shirt and having clean shoes. We both thought it was a funeral when we walked in at first.
So that's why I suggest something other than monochromatic for a wedding you'd be a guest to, if this is the case. But I'm still new to the style thing here so take my word lightly.