Former Central Intelligence Agency director Richard Helms and his successor, William E. Colby, carried their bitter, personal feud into the open yesterday by sharply disagreeing on what public activities the CIA should be permitted or directed to undertake. w

The forum for their conflicting views -- which even included the exact mission of the agency -- was a hearing of the subcommittee on oversight of the House Permanent Select Committee on Intelligence.

The two men, once close colleagues, had to testify separately because Helms refused to be in the same room with Colby, according to a committee member.

Helms publicly has accused Colby of damaging the CIA by turning over agency records in 1973 and 1974 to administration and congressional investigators. He is particularly bitter that information from Colby launched the Justice Department investigation into the allegation that Helms committed perjury before a Senate committee when testifying about CIA activities in Chile. He later pleaded "no contest" to two misdemeanor counts of failing to testify fully and accurately before the committee.

Yesterday, the focus of their attention was the future role of the CIA, although the immediate subject for discussion was whether the intelligence agency should declassify and release to the public its reports and analyses.

Helms, the traditionalist, argued "this agency [CIA] wasn't established to keep in touch with the public." He said he hoped it would return to the old days when its activities were secret.

Colby took the reverse tack. "The modern American intelligence community simply cannot be treated as a traditional spy service whose very existence was denied by the monarchs it served," he said.

To Colby, the CIA has a mission to "know what's going on in the world around us" and the responsibility to pass on its information to "the entire American government," including the Congress as well as the president. At times it could go even to the American people.

To Helms, however, the agency's mission is "as staff to the president" and no more. "Its job is to advise the president and the [national security council] . . . stay out of the limelight and keep quiet."

Helms agreed "times have changed" but added that he is still "a bit old-fashioned."

Rep. John Rhodes (R-Ariz.) referred to Helms' views in questioning Colby by tactfully attributing them to "one of your predecessors. . . ."

But Colby, who entered the hearing room only moments after Helms' departure, snapped his response to one question with a barb that indicated he knew the source.

"Many would like to go back to the zero secret game," Colby said, "but they haven't caught up to what the new information game is all about."

Helms argued that published reports by the CIA would not help the agency's standing with the public. "I don't understand why it adds to [the agency's] credibility to put out such things," he said, adding that it would involve the agency in politics and could "give insights to the Russians that they would be delighted to have."

Colby, on the other hand, said "the agency needs to do a better job of educating the public" because "an informed public is an essential element of any national policy." For Colby, the intelligence concept of "need to know" as a criteria for allowing someone access to information "compels the wide distribution" of declassified CIA material.

Colby went so far as to suggest that satellite photographs of Soviet missiles and other military systesm eventually should be made public, because the government already releases other basic data about those weapons.

One of their basic disagreements came over the CIA providing material in response to inquiries from the press.

Helms said that he believed agency officials "simply don't provide the information" when asked, but his answer left out officially authorized leaks that occurred when he was at the agency.

Colby criticized that technique by which CIA once gave classified information "to those favored journalists given background briefings."

In its place, Colby suggested that the CIA find a way to release "news item" information, such as finding the so-called Soviet brigade in Cuba, in a way that would permit such subjects to be "presented in their true proportions, and minimize the excess rhetoric from various sources which characterized the [recent] incident."

On one aspect of releasing basic CIA information, the two former directors seemed to agree: Economic, industrial and agricultural statistics developed by CIA should be made public through other executive departments.

Perhaps the sharpest difference between the two on what was called the "post-Watergate CIA" was drawn on a question about how to handle CIA information that undermined a presidential policy.

Helms told the subcommittee: "I don't believe a CIA director should give information that could be used to oppose" an administration policy. If he were asked for such information at a congressional hearing, Helms, with his own past clearly still on his mind, said, "at that point a director prays." h

When asked the same question, Colby quickly responded that the information should be given out "even if it doesn't support . . . policy." If it is good information, Colby said, "hopefully it will help change the policy."