Well I wore a white skirt and a colourful top with no problems whatsoever. I think it'd be ok if it's very hot and it's just a summer outfit as opposed to a full on ball gown or anything like that... I'd still ask the bride tho most likely.
I wore a white suit last Friday at a wedding I went to. Didn't even think about it - never have thought about it. Would people have been thinking bad things about me for wearing white?????
Lots of young girls wear white suits. Mel B when she got married asked that all guests where white. I'm sure as long as you dont wear a big dress and a tiara its fine.
Apparently as far as tradition goes, its the bride who wears all white (obviously white trousers/skirt with a colourful top is a different matter) Its her day, a white dress is what makes her stand out from everyone else. But as a Mother In Law, tradition states that its the biggest insult to the bride, if the Mother in Law wears white. Its meant to be she is trying to out do the bride, and taking the lime light off her.