Even though it's just a jacket, I try to avoid white or cream on top in large amounts, at weddings. It's tough, because summer events just call out for white toppers!
Pashminas are more trouble to me than jackets, but have the great advantage of the huge array of colors available. I;ve used silvery-gray wraps with raspberry before. Or some form of gold, as Bea said--just the right yellow, with raspberry and cream, has a nice summer floral look.
Navy could also work--even a jacket, such as a navy linen. A lot depends on the actual look of the lace dress, such as how dressy-formal, and your coloring.
