Charcoal Grey Prom Dress Dark Grey Tulle With Lace Applique Sweetheart Long Prom Dress, A Line The Girlfriend's Guide to a Formal dress code. Reserved for elegant evening events, this dress code is less formal than Black Tie but more formal than Cocktail. Women should opt for a Vocal Gabriella Lace Trimmed Slip Dress Charcoal Small Charcoal Slit Back Charcoal Grey Maxi Dress Cocktail Attire Guide for Women: 8 Essential Dos and Don'ts Couture Candy