i never really understood 'dressing down' at weddings, until i was a bride. i would always want to look my best for every wedding and would freak if my dress or tan wasn't right, etc. then i became a bride and realized it was all about me on that day-not my guests.
on my wedding day i didn't give a rat's toosh about what others were wearing......people wore black to my wedding and i didn't care, hey my cousins didn't even wear ties or jackets. (it wasn't blacktie but was formal)
anyway i see no issues with black, i've worn it to a lot of night time weddings, not always black tie. I do usually have a nice coloured wrap or accessory to go with it.
i did wear a black and white dress here in the UK and i didn't stick out, but i would have been better off in my pink dress......but i will admit it made me feel skinnier than the pink dress and i wanted my husband to be proud of me on that day....i guess i was being vain, but it wasn't about outshining the bride. it was about looking good for my husband.