The one wedding etiquette rule for guests is to never wear white. Of course, there are some exceptions in different cultures, but in most Western traditional weddings, white and its shades are reserved for the bride. Knowing this, a woman chose a yellow dress as a wedding guest.
But, when the party got in full swing at the end of the evening, the lights went down and black lights came on, the dress appeared white. A person then approached the woman and asked her to leave. Thinking this was ridiculous, she refused and stayed. Still, she wanted to check: was she being inappropriate?