Never wear red, the bride will be unhappy. Red belongs only to the bride of the day. You can't wear white, which is not the same color as her wedding dress. Generally, ask the bride what color her dress is on that day, and try to avoid these colors. Generally, you can wear a formal little dress, which won't steal the bride's thunder, because she is the most beautiful that day, and you can't steal it, but if you dress formally and appropriately, she will have face. If it is a Chinese wedding, she can wear it.