Hubert de Givenchy, whose designs turn women into art, was the center of attraction at a benefit last night for the projected National Museum of Women's Art in the gilded grandeur of the Departmental Auditorium.

There were as many Givenchy dresses on the guests as there were in the exhibition of 30 Years of Givenchy Couture, turning the room into a moving show of his creativity.

Among guests were two of his best known clients, Bunny Mellon and Deeda Blair. Clothes that had been worn by both were in the exhibit. Few of his clients, however, have had the kind of service that Blair had this morning. "Hubert came over at 9:30 this morning to the house to be sure my gown was fitted right," she said. "He is an old friend and I was one of his first customers in the 1950s." The dress, a pale violet, was worth the effort, those surrounding Blair said.

Bunny Mellon, who, with her husband Paul is the chief supporter of the National Gallery of Art, came to the event last night even though a car ran into her car yesterday and she was somewhat shaken up. "But we won't think about that anymore," she said. "I'm so glad to be here." Three of her evening coats were on exhibit.

The Departmental Auditorium, transformed into a palatial ballroom for the evening, is decorated in high 1930s style. It was a new place to have a benefit. Longtime Washingtonian Dorothy Marks, wife of attorney Leonard Marks, said this was the first time she remembered having a party there in all her years in Washington. Malcolm Baldrige, the secretary of commerce, was master of ceremonies.

The dinner was one of a series of events in what might be called a Givenchy festival. Monday night, Deeda and William McCormick Blair gave a dinner for 53 in Givenchy's honor--complete with table cloths and napkins made of Givenchy fabric. French Ambassador Bernard Vernier-Palliez gave a luncheon yesterday for the designer.

At lunch, the ambassador raised his champagne glass at a table surrounded by women wearing Givenchy dresses, where every course could have been a still-life picture. But Vernier-Palliez said that the French weren't always happy with the image of France as the country "of good food, pretty ladies and great fashion."

"Sometimes we think we would like to have other countries think of us instead as a modern industrial country," said Vernier-Palliez, who as a former head of the Renault company accomplished a great deal in that direction. "But though it is nice to have a modern image, it is good to remember our country's traditional strengths, and fashion is certainly one of the most important. Fashion is art and culture and we have no better ambassador to the world than Hubert de Givenchy."

At the luncheon, not quite half the women wore Givenchy dresses of varying vintages. Wilhelmina Holladay, the founder of the National Museum of Women's Art, which is due to open in three years, was one of them. Hubert de Givenchy looked her over with approval, and then removed an almost invisible thread from her skirt.

Denise Vernier-Palliez, the ambassador's wife, and Bunny Mellon were honorary cochairmen of the evening benefit.

Blair said she missed the dress of hers that is in the exhibit. "I told Hubert I must have it back soon, I can't do without it." Blair was wearing one of his designs for lunch--one that she had ordered with a suede jacket instead of velvet and a slightly different skirt. "I'm one of the few who is allowed to make changes," she said. "He was surprised when he saw me in it."

Givenchy himself was not wearing a Givenchy at the luncheon, though there are Givenchy men's clothes. "I order my flannel suits from London. They are good cutters for men. I like very conservative clothes for men. For a man to be fancy is to be ridiculous. The cut, the fabric, that is important. I feel uncomfortable to look like a dress designer."

Comfort, indeed, is indispensable in dressing well, he said. Reminded that he once said Bunny Mellon is the most elegant woman in the world, he pointed out, "When she gardens, she wears a jean skirt. That is right. She came to help me with my garden--you know she is a very great garden designer--and my gardener was amazed that so great a lady would herself dig in the garden and put fertilizer on the flowers, all without the gloves."

The benefit seemed to be evenly divided between fans of Givenchy and the art community. Among the art group were gallery owner Harry Lunn, Adelaide Breeskin, an associate director at the Museum of American Art and John Bullard, director of the New Orleans Museum of Art.

Holladay said the benefit was attended by 660 persons and raised more than $100,000 for the planned museum.