What do you look like, too?
I would personally wear a nice, slightly heavy-fabric dress in a darker lavender or a darker blue and carry a nice shawl or cardigan. Something a little shiny. I'd go with heavier fabric, because it's still going to be cold. Make sure your dress doesn't match the bridesmaid's dresses, too.
Closed-toed shoes, because you'll probably want to wear hose and they don't look right with open-toed shoes.