The audience, by request, wore black and white to watch good and evil battle it out at Arena Stage at last night's 35th-season gala opening of Bertolt Brecht's "The Good Person of Setzuan."

"First feed the face, and then talk right and wrong," Brecht once said. His advice was followed twice last night, with drinks and food served before and after the play for some 400 friends of the theater. Some conversational tidbits:

"I think Brecht would have been very surprised to see us here dressed so in black tie," said Dr. Gerhard Herder, the East German ambassador, there with his wife Edeltraut. "I met him in the 1950s in Berlin. He was a modest man, always very modestly dressed in pants and a shirt -- he never wore a tie."

Austrian Ambassador Dr. Thomas Klestil, who attended with his wife Edith Marie, said he felt the same way -- "all those poor people in rags on the stage, and all the audience in jewels and fancy gowns."

Franz Bader, founder of the art gallery, said, "I remember vividly going to see Brecht's Viennese premiere of 'Dreigroschenoper' The Threepenny Opera with the Nazis demonstrating outside. It must have been 1936, '37." Shortly afterward, Bader immigrated to Washington.

Herder said that Brecht's theater and his house and library are big tourist attractions in East Berlin, where the playwright lived in the last years of his life before his death in 1956. "His plays are produced all the time."

Klestil said Brecht isn't so often staged in Vienna. Both Herder and Klestil said they thought the Arena Stage version was very good, right down to the translation.

Journalist Henry Brandon said he met Helene Weigel, Brecht's last wife, in East Berlin. "She was very critical of the East German government, but she didn't want me to quote her."

Walter and Joan Mondale, she in a classy white evening suit, were out on the town again in what seems to be their return to the social swim. "It's good to see old friends," said the former vice president and presidential candidate. "But we don't want to go too much." Both Mondales remembered when Arena had far less palatial quarters. "They've upscaled," Mondale said, with his characteristic wry grin.

Ah, those original premises: Zelda Fichandler, producing director of the theater, said she remembered them well. Everyone remembers the brewery, when people joked about it being the Old Vat, as contrasted to England's Old Vic, but Fichandler said, "We had another theater before then. We started in 1950 in an old movie house at Ninth and New York. A real slum neighborhood. It was 30 by 36 feet but we got 247 seats in it."

Back to this season: "I'm proud of the company." In the spirit of anniversaries, Fichandler said, her gold satin blouse was one she had bought "for the opening in 1966 of 'The Wall.' "

At curtain call, Stanley Anderson, who plays one of the gods, began a round robin of tributes to Zelda and Thomas Fichandler and Arena President Lee G. Rubenstein. Thomas Fichandler, after 35 years, is retiring as executive director. "I'll still continue to raise money for Arena," he said in the receiving line before the performance. "But now I'm going to consult with other theaters across the country, showing them how we solved some of our problems."

Rubenstein added that Arena has raised all but $2 million toward its current goal of $6 million for a matching NEA grant.

Between bites of schwarzwa lder torte, amid glowing remarks about the performance, one person, reflecting on the serious themes of the work, said, "It's a gala party, but not a gala play."