"I think Daniel Terra could be cast as Santa Claus -- it's his warm and twinkly eyes," said Robert Keith Gray. He could have mentioned other Claus-like attributes--Terra's white hair and mustache and his habit of giving not only paintings to museums but museums to cities.

Last night Gray, the longtime Washington public relations man, gave a formal dinner for Terra, the first American ambassador at large for culture, at the exclusive F Street Club.

Said Gray: "I first met Dan during Ronald Reagan's campaign. He did a marvelous job of raising money. He's so good at his current job because he really knows how to make corporations give money, for one reason because he gives so much himself. You know, he's building a $20 million American art museum in Chicago--that's his second. He already has one in Evanston, Ill. And last July he paid $3.25 million for Samuel F.B. Morse's 'Gallery of the Louvre' painting. You know, it's a funny thing about that painting. Morse tried to exhibit it for money but nobody would pay to see it. Shame he didn't know Terra."

In reply to a toast by Gray, Terra joked, "I've never had such nice things said about me, but they're true as can be. But I want to tell you that what I say is my own stuff. I don't have a big organization like Gray to write my speeches for me. Have you ever been up to see Bob Gray's office, in the Power House? They make so many mistakes up there that they have to have that great big incinerator outside. Just a shredder won't work for them." (Gray's office is a converted power plant in Georgetown.)

The F Street Club is one of the three or four places in Washington where parties are given by people who 40 years ago would have kept mansions and large staffs. Its dining room seats only 50, and they all must be close friends to fit.

Guests last night dined by the light of tall white candles. The menu was lobster bisque, roast beef, endive salad and Grand Marnier souffle'. The guests drank champagne from soup to dessert.

Ralph Becker, well known as a gourmet chef, said, "My wife and I have completely changed our way of eating in the last few years along with Craig Claiborne and James Beard. But when we come out to events like this, I can't help but be tempted. Do let me send you my recipe for a low-calorie baked potato."

The guest list was the top layer of Washington's culture cake, with a few politicians, diplomats and Washington socialites sprinkled through like plums: J. Carter Brown, director of the National Gallery, and his wife, Pamela; Roger Stevens, head of the Kennedy Center, and his wife, Christine, who came despite a broken ankle; Charles Z. Wick, director of the United States Information Agency, and wife Mary Jane; Katharine Graham, chairman of the board of The Washington Post Co.; and Jayne and Frank Ikard--Jayne Ikard just back from making a movie in Ireland.

Builder and developer William Cafritz looked around and said, "This city is pretty well run by the people in this room."

The ambassador of Luxembourg, Adrien Meisch, who is well known as a concert pianist, looked at the piano in the drawing room and said, "I will do all sorts of other tricks, but tonight I will not play." His wife, Candace, who is a singer of note, said, "Well, I would sing, but he won't play, so . . ."

Clare Boothe Luce told another guest how the spelling of her maiden name was changed. "My grandfather, William Franklin Booth, attended the Baptist Seminary here in Washington. After Lincoln was assassinated by John Wilkes Booth, my grandfather added an 'e' to his name, and ever after, on Lincoln's birthday, he gave a sermon about Lincoln and told the story about why he added the 'e'."

Luce wore the ribbon of the Medal of Freedom on her evening gown. She received the award Wednesday from President Reagan.

And Terra was pleased to say, on this night of being congratulated for his contributions to culture, that he had bought yet two more paintings, "two of the greatest American images ever painted, Sanford Gifford's 'Hunter Mountain' and Fitz Hugh Lane's 'Brace's Rock, Brace's Cove.' "