Can we discuss some silly etiquette now? We all understand why you're not supposed to wear white as a wedding guest. It's a little bit dumb, but understandable nowadays, when one can never tell just how formal/traditional the bride is going to be. You wouldn't want to show up in a white tea-length sundress, when the bride is wearing the same thing (embarrassing for one, annoying for another). That rule about not wearing black to a wedding has fallen away because, well, that black is formal, easy, and looks good on everyone. But somehow you're still not really supposed to wear red to a wedding -- or rather, you should "use discretion."
I remembered this trivial bit of etiquette last week as I put on a red & white floral sundress to wear to a friend's wedding. It's a pretty little sundress, and no one would have confused me with the bride. Still, I vaguely recalled the red rule and changed dresses just before leaving the house.
I think it's just more anti-redhead discrimination. So I say to my own wedding guests who may be reading, feel free to wear red. Or white even. Just wear something loose because it's gonna be HOT!