Swedish National Day is a recent tradition. It was established as late as 1983 and at the same day the Swedish national costume was introduced by no other than Silvia, queen of Sweden.
Thus at the Atlanta celebration some women, including the honorary consul of Sweden in Atlanta, wore the most recent version of the Swedish National costume.
Many more people, however, both men and women, tried to incorporate in their clothing the colors of the Swedish flag: blue and yellow, because Swedish National Day was previously celebrated as Swedish flag day.
Thus the party was full of guys in navy blue suits with either yellow shirts or ties and ladies in blue and yellow dresses and ensembles. The room was really blue and yellow, or as the Swedes say "blaagul" when they mean quintessentially Swedish.
Songs were also very Swedish, and so was the food served at the party:smoked and marinated salmon (lax),
Jansson's temptation (a baked dish of matchstick potatoes and anchovies with onions and cream),
Swedish meatballs with lingonberry preserves,
crisp bread and cheeses.