When the day arrives, you walk into the reception and notice that the color of your dress is the same as that of the bridesmaids. Suddenly, you feel uncomfortable, and many thoughts come rushing to your head.
The truth is, you can wear a bridesmaid outfit without violating etiquette or wedding dress codes. As long as the dress is not too similar to the bride's and the bridesmaids.
All-black outfits are generally worn to a funeral. Unless you're specifically required to wear all-black attire, you should avoid this color at all costs.
As long as it doesn't violate any etiquette, rules, or dress code, you are free to wear any outfit you want. As a guest, you have the freedom to express yourself more than the bridesmaids.