This article is more than 10 years old. Your office Christmas party is a great official event to dress up for. But it's not always easy to decide on what to wear and how formal you're supposed to be.

There, glaring in red and green at the bottom of the holiday party Evite, lurks the season’s most vague directive: “Dress festively.” Even Lizzie Post, the co-author “Emily Post’s ...

How to dress festively — Oscar de la Renta's 2013 resort collection featured an elegant green formal dress, perfect for a black-tie party.