Of all the occasions for which one might wish to “dress up”, the Cocktail Party is one of the few that has, perhaps, the least ambiguity. Like many other social events, the traditions for Cocktails hails from an earlier era of well-heeled socialites enjoying each others’ company, in this case to enjoying alcoholic libations in a less formal setting than dinner would demand.
Obviously, the situations have changed over time, and it is rare that those attending a Cocktail Party are ducking home to change into their Black Tie outfits for dinner, but there is something of a progression from “work” attire – even in the suit-centric industries – and what is Cocktail attire.
As is often the case in these tradition-structured events, most of the “rules” are for what the men are wearing, and in this case it is just a bit more formal than standard corporate business wear. For guys, pretty much across the board the recommendation is for a dark suit, from dark blue through a medium dark gray, with a white or subtly colored (cream) shirt, a subtle tie, optional pocket square, and appropriate footwear. This varies only slightly from “semi-formal”, and is likely to not be much of a shift from many big-firm lawyers’ daily gear. There is some variation of opinion on how far from “a dark suit” one could go, but this is clearly a case of knowing your hosts, and failing on the side of conservatism if one has doubts if that clan tartan suit is going to fit in rather than a subtle charcoal-on-charcoal herringbone.
For the ladies, this is almost as easy, as it’s the classic venue for the “little black dress”, with the addition of having the option for more “showy” versions than might be appropriate in more formal settings, with rhinestone, lace, and embroidered accents. As far “showing”, this will typically be sleeveless and knee-length, and can be executed in any number of colors. One probably would want to avoid “loud” patterned fabrics, but the whole spectrum of basic hues (season permitting) is open in this context, as are more dramatic designs. The Cocktail Party is also open to less-formal (office) attire such as skirt and dress shirt, dress pants and dress shirt, and similar parallels to the men’s work outfits.
Of course, with the creeping informality in society, what has been traditionally meant by “Cocktail Attire” may, in any given situation, have far more latitude than detailed above, and what is meant to be suggested by it in New York or Washington, might have a quite different meaning in Miami or Los Angeles. However, going with dark suits for the gents, and “little black dresses” for the ladies will keep the look classic for the event.