They turned on spotlights just like the red, white and blue ones that light up the Eiffel Tower. Only this time, they lit up the celebration of another one of France's towering monuments, the elegant and tall--6-foot-6--designer, Hubert de Givenchy.

Audrey Hepburn, who made his designs visible to many through such films as "Sabrina," "Funny Face" and "Breakfast at Tiffany's," paid tribute to her 30 years of friendship and collaboration with the designer: "Hubert is like a tree--tall, straight, the roots of friendship always strong, the wide branches of his affection sheltering everyone. Hubert, perhaps, has not all that he loves but he loves all that he has."

This is the 30th year since Givenchy opened his couture house in Paris. Many of his clients joined in a gala celebration at the Fashion Institute of Technology tonight, including those who are his special friends, Hepburn, Bunny Mellon and Deeda Blair. Among the more than 900 other guests were designers who came from California, Rome, Paris and up the street on Seventh Avenue, retailers and just plain admirers. The evening began with a cocktail reception opening the retrospective exhibition, and then moved across the street for the fashion show followed by a dinner with French champagne.

"Givenchy represents elegance at its best," said designer James Galanos, who bought two tables at the benefit, which is expected to bring $200,000 to the school's scholarship fund. "He has retained that quality all through his career, which is really beautiful." With Galanos was Connie Mellon, who was wearing a red Galanos. "They are the two greatest designers. It was a terrible choice to have to make."

To enter the building housing the Givenchy retrospective of a hundred of his designs, guests had to pass inspection of crowds of FIT students held behind barricades. They cheered when Givenchy made a brief appearance, and they recognized and applauded Galanos, Issey Miyake, Mary McFadden and Michaele Vollbracht. "I'm waiting for Audrey," piped up one student in a red mini.

As the black-tie and gala-gowned guests crossed the street to another FIT building for a fashion show of Givenchy's spring couture collection, it was Oscar de la Renta who caught the student crowd's attention. "I'm a Givenchy friend first, and I'm also a fan," said de la Renta, who was wearing a dark suit and who shook hands with some of the students.

The all-star crowd included French actress Capucine, Betsy Bloomingdale with Jerry Zipkin, Estee Lauder, Pauline Trigere, Tammy Grimes, New York Gov. Hugh Carey and his wife, Evangeline, French designers Philippe Venet and Jean Cacherel, Fran Stark, Sao Schlumberger and Arlene Dahl.

Hepburn had been expected to attend a dress rehearsal that afternoon, but students waiting to see her were disappointed. "It was 90 percent. If Audrey was here, it would have been a hundred percent," said FIT student Gerard Dellova, from Brooklyn.

Planning the retrospective, which is on view through Oct. 2, and reviewing the clothes he made for the Duchess of Windsor, Jacqueline Onassis, Princess Grace and others inspired the spring couture collection, Givenchy said before the show. Models dashed up the aisle of the auditorium onto the stage and stood before a full-stage-sized photograph of the Givenchy couture house. They slipped behind the slatted screen and the picture melted into a film that showed those same models behind the scenes at the Givenchy show in Paris. The audience liked most the blouson suits, the tunic dresses and the long, sexy fitted gowns with generous ruffles up the back, on the sleeves or at the hem.

Tonight's show incorporated dancers, models, brief film interviews with the designer and film clips from Hepburn movies for which Givenchy made her clothes. Then the actress appeared in a lean, black ruffled Givenchy gown and took the microphone. "Thirty years of Hubert. Thirty years of genius. Thirty years of friendship," she said. "Thirty years of infinite integrity." She then went to the side of the stage to bring out the clearly embarrassed designer, whom Hepburn could not resist hugging and kissing as they stood together for photographs and cheers from the audience. He responded with a brief, quiet thank you in French.

In a clip during the fashion show, Givenchy said, in perfect English, "After 30 years I am still learning. I am never satisfied." He may not have been, but his guests last night certainly were.