They thanked Luck and God, six stars from the movie "The Color Purple," as they stood in front of a cheering audience at the close of the film's Washington benefit premiere last night. It isn't every day, after all, that Steven Spielberg, the prince of pyrotechnics, takes on something as terrestrial as "Purple" and potentially boosts the careers of up to 20 black actors.

Author Alice Walker and star Whoopi Goldberg were not present (they were at another benefit premiere in San Francisco), but standing there in front of the Tenley Circle Theatre screen, minutes after they had just been seen on celluloid, were Margaret Avery, Oprah Winfrey, Willard Pugh, Akosua Busia, Rae Dawn Chong and Susan Beaubian, introduced by Gloria Steinem.

Then the actors adjourned to the reception downstairs, soon to be inundated in a sea of purple as scores of audience members plied them for autographs with opened programs of that shade.

"The sense of unity was there," said Chong, who plays Squeak, trying to talk about the movie between signings. "We all cared so much for each other." And Spielberg, she said, was "great."

"I'd jump over the Grand Canyon for him," said Beaubian (Corinne in the film) of the director. "He's a doll. He can get the best out of you." The movie is not about black identity, she said, but "about finding yourself as a human being. Realizing how important it is to know one is loved."

"Do you have a ball point?" Avery (Shug) asked one of many autograph hunters in front of her. "This one won't work." Then back to the movie: It's about "discovery," she said, without taking her eyes away from the purple page. "Self-discovery."

"V as in Victor," insisted another autograph hunter, waving a program at Avery.

"What's his name?" asked a besieged Winfrey, thinking she was signing a program for yet another absent relative.

"This one's for me, 'Mary,' " said a Mary.

"This is not a black film," said Winfrey, who drew the loudest applause from the audience for her feisty portrayal of Sofia. "It's about endurance, survival, faith and ultimate triumph. Whatever you want is in you."

Steinem, too, was reflecting on "Purple." When she introduced the film, she told the audience, "The people sitting in front of you and next to you will be bonded to you for the rest of your life. This movie sorta moves your heart around, breaks it and brings it back to life again. It's a sort of a heart augmentation operation."

Proceeds from last night's showing benefited the Ms. Foundation for Education and Communication (of which Steinem is chairman of the board) and the National Political Congress for Black Women, chaired by Shirley Chisholm (who was represented by C. Delores Tucker). "Your money," Steinem told the audience, "is going for making women visible politically and giving them a voice politically, and giving women a voice nationally through the pages of Ms. magazine . . ."

The relationship between the National Political Congress and the Ms. Foundation for Education and Communication is a "spiritual connection," Steinem said earlier. "We are both concerned with helping women to decide their own lives. It just seemed natural" for both entities to cosponsor the event, she said. "Shirley Chisholm is a friend and colleague . . .

"The movie means more to me than any film I've seen. It shows real people's lives, because it understands the problems of race and sex and class all at once. I don't think it's possible not to leave the theater a changed person."