A Hollywood crew began shooting the film version of "Born Again," Charles Colson's Watergate-to-Salvation saga, early yesterday morning. But first they gathered with Colson at the Key Bridge Holiday Inn to receive breakfast blessings and prayers for the film's success from a Catholic priest and a presbyterian minister.

The plan is to do four or five days of outdoor filming here and then to make the rest of the movie in California, where interior sets have been constructed. They began yesterday at a place described in the script as "the back of the Senate building."

What Senate building? The Dirksen Senate Office Building? The Russell Senate Office Building?

When actors, directors, producers, crew, extras and wardrobe people arrived at 8 a.m. to film in the rain, the place they meant to use turned out to be the United States Capitol. And not the back of it, which faces the White House, but the East Front, where presidential inuagurations are held.

"These Hollywood guys don't know the back from the front," said Margaret Shannon, a former Senate aide who had been hired as a liaison. "It's easier for us to let them call it what they want."

What they want is the Washington that Hollywood knows best - the scenes of lawmakers strolling down the Mall, or looking out the window at the Washington Monument - and if they have to turn the Capitol around to set it, that's all right.

There they were yesterday, Colson (played by Dean Jones) and his law partner Dave Shapiro walking home down the Mall after a hard day on the Hill with throngs of Hollywood electricians, cameramen and costumers watching this slice of Washington realism.

Another scene takes place in the Jefferson Memorial, where Colson takes his children for a quiet stroll to talk over in privacy whether he should plea bargain. But no Washington in the history of the city has ever gone for an afternoon's family stroll in the Jefferson Memorial without an out-of-towner in tow.

"Maybe, but that's what people around the country want to see of Washington," said production designer Bill Kenney. "We take a little artistic license."

Kenney said he's most proud of the authenticity of a reproduction of Colson's Executive Office Building office in California. "I'm anxious to see Chuck Colson walk in there."

In the exterior scenes, he walks in from 17th Street, instead of West Executive, because the White House will not permit filming inside the grounds.

"But it looks the same, nobody will know the difference," he said. From the office window a view of the White House as seen from the South Lawn will be visible. "You need a big transparency for that, and it is so happened that the only one in Hollywood shows the White House from the Ellipse. People won't know the difference."

Another scene to be made here shows Colson and his wife attending St. John's Church. "He did not technically go to St. John's - I believe he goes to Columbia Baptist on Lee Highway and Patty goes to St. Luke's on Rte. 193 - but he is an Episcopalian," said Shannon. "It was a good opportunity to show Lafayette Square."

And that, said the Washington location coordinators, is the key to all those scenes in Washington movies that look odd to Washingtonians but just fine to the rest of the country. Who else is going to know that the Kramer Books & Afterwords apron worn by a film news dealer refers to a store that didn't exist in 1972, when the film takes place?

"They all come here wanting the same scenes," said Stuart Newmann, whose firm sets up the shots, gets the necessary police permits and arranges for local crew and extras in nearly all the films made in Washington.

"They want the White House scene, the Capitol, maybe th memorials - picture-postcard Washington. Not one movie has ever had a scene that wasn't in Northwest, because that's the part they think of as Washington. And there's never been a woman star in them, because they all see Washington as a city of men."

"We suggest other places, but nobody's used them yet," said his partner. David Siegel. "But we never tell them. 'Look, this has been done a thousand times.'"

It all has, though. Just when Bill Fitzgerald, a white-haired extra, was recalling which other films had had him standing in the same spot, looking his same distinguished look, executive producer Robert Munger came up and said. "You're my idea of what a Senator looks like."

Munger nodded. He'd been told the same thing by the people who hired him for "All the President's Men," - F.I.S.T." "The Secret Files of J. Edgar Hoover." "The Greek Tycoon." "Advise and Consent," and probably some others, he said, whose name she couldn't recall.

"There's one scene they all want - the President in the back of his limousine, entering the White House through the Northwest Gate, or leaving it through the Tourist Gate", said Newmann. "Now of course, we all know that the President comes in the Southwest Gate, but that's not what they want."

"Then they like to have people coming out of the Capitol as they start a conversation, and finish the talk a few minutes later in fron of the White House people talk to each other in Lafayette Square."

They don't get the White House front door because of the regulations there, but the other two scenes usually get in.

"The movie people always say it doesn't matter what's true - its what people think is true that's important," said Neumann. "I guess they're right."

Neumann and Siegel have set up these sort of shots for "Behind Closed Doors." "The Other Side of Midnight," "Ben and Muggsy," "The Happy Hooker Goes to Washington," "F.I.S.T.," "The Greek Tycoon," "All the President's Men," "Three Days of the Condor," and "Eleanor and Franklin."

Meanwhile, the "Born Again" people were observing the rules of Hollywood and the special ones of this production very carefully.

The blessing beforehand, said producer Munger, is "something I always do. Alfred Hitchcock always put himself in his pictures, and I always have prayers for mine. It's like the Notre Dame team being blessed before the game."

Munger is a born-again Christian, as is the film's star, Dean Jones - whom Munger selected partly for that reason - and former Senator Harold Hughes, who will play himself in scenes to be shot later in California.

Colson did not attend the first day's filming - Jones had said it would make him nervous - but arranged for the crew not only to have their breakfast blessing, but to attend a screening of a film made by Prison Fellowship, the rehabilitation group to which he is donating his film money.

Wherever the filming went, streets were blocked off and a convoy of trucks and mobile homes moved in. "You see," said production manager Russ Saunders, a former football star at the University of Southern California, who started in films as an extra in sports movies, "we in Hollywood have our traditions. We always put out coffee and pastry for everybody.The mobile homes, Jones gets one to himself, and Anne Francis gets one to himself, and Anne Francis (who plays Mrs. Colson) gets one, and there's one for the director (Irving Rapper) and one that anybody else can use.

"And I put out the chairs. Some of them we brought from Hollywood, and some we got here, but we brought the stencils to have the names put on them. You see, it's important to get this right."

"In Hollywood, we have a lot of protocol."