On the first stop of his 10-nation Caribbean tour, U.N. Ambassador Andrew Young told a group of Jamaican students: "Some of us are still kind of amazed that we're now representing the government when a few years ago we were considered anti-government."

It was a statement that applied not only to Young, the most outspoken and controversial member of President Carter's foreign-policy team, but to several of the people accompanying him on his whirlwind trip to dramatize the administration's new policy of priority attention for the Caribbean.

Most of Young's backup team are the sort of young professionals - officials of the State Department, the National Security Council and the agency for International Development - who traditionally go along to provide a traveling bigwig with the facts and figures of foreign-policy expertise. But at least four are among the most unlikely diplomats ever to hit the road on behalf of the U.S. government.

They include Sam Brown, a leader of the 1960s antiwar movement who now heads the Peace Corps, and Brady Tyson, who earlier this year apologized to an international human-rights conference in Geneva for past U.S. actions in Chile - a move that earned him both headlines and a hasty repudiation from Carter.

Then there's Stoney Cooks who has moved from dodging sheriffs in the South to carrying a briefcase crammed with top-secret documents, and Sally Shelton, who looks more like a campus homecoming queen than a young woman who had just been tabbed as one of the top planners and executors of U.S. Latin American policy.

he four are by no means alike in their backgrounds or in the attitudes and perceptions they bring to their new jobs, but they are representative of the Carter administration's attempt to bring youth and the ideas forged in the civil rights and antiwar movements of the past decade into the formulation of U.S. policy toward the countries of the Third World.

Of them all, the best-known is Sam Brown, whose role in mobilizing student opinion against the Vietnam war chapter of recent American history, helped produce the most turbulent. He is also the ideological of the group - a self-professed radical who looks back nostalgically on his activist days and wonders aloud about bear on what he regards as the many how to best bring the same spirit to ills that still linger in American society.

Although he still refuses to wear a necktie, Brown has taken to working within the system in recent years. In 1974, he got elected state treasurer of Colorado, and early this year, he accepted Carter's invitation to become head of ACTION, the umbrella organization for federal volunteer groups including the Peace Corps.

Despite being a member of the team, Brown says he had reservations about "the caution and fiscal conservatism" of the Carter administration. In fact, he came along for the first leg of the trip primarily because of his interest in Jamaican Prime Minister Michael Manley's efforts to promote radical social and economic change through socialistic methods.

He is especially fascinated by Manley's program of mobilizing Jamaican youth into a national service corps that assists with literacy and agricultural development projects. When Young left Jamaica, Brown stayed behind for a closer look at whether action could make use of the Jamaican ideas and techniques.

"Coming down here isn't just a case of seeing what we can do for Jamaica," he said. "The Jamaicans have a lot to teach us, too."

Almost matching Brown in ideological intensity is Brady Tyson, 49, a political adviser to Young who was largely unknown before the controversy touched off by his apology for alleged U.S. attempts to "destabilize" the government Salvador Allende, a Marxist, in the early 1970s.

That caused a lot of conservative commentors and congressmen to look up Tyson's record. What they found led to several of them to charge that Young is harboring someone akin to a bomb-throwing anarchist within the U.S. mission to the United Nations.

The charges do not bother Tyson, who has been getting involved in controversies ever since the 1960s when he went to Brazil as a Methodist missionary and wound up being expelled by the military regime there because of his alleged attempts to stir unrest.

After returning home, Tyson hooked up with the civil rights movement in the south, becoming a friend and admirer of Young. The relationship followed after young came to Washington as a Democratic congressman from Georgia, and Tyson, then teaching international relations at American University began feeding him ideas on foreign policy.

Tyson, makes it clear that his loyalties are to Young and not to the traditional Washington foreign-policy establishment. He is openly contemptuous of most U.S. career diplomats and the press, both of whom he accuses of helping to keep repressive regimes in power throughout Latin American.

"I'm here because I want to be of service to Andy Young in any way that I can," he says in the nasal twang of his native Texas. "I believe there's nothing more important than human rights and I think that Andy Young who learned all about how to fight for human rights in the U.S. civil-rights struggle, is the man who can test transfer those lessons to the struggle for human rights in other countries.

Similarly devoted to Young is the ambassador's longtime aided Stoney Cooks, whose casual, laid-back style masks the talents of a natural-born organizer and fixer. Cooks, 34, is another veteran of the civil-rights movement, who originally went to South as a volunteer in 1965 after dropping out of college.

He stayed to become a key operative of Young. Hosea Williams and other leaders of the Southern Christian Leadership Conference. Among the many chores he performed for SCLC was masterminding the black voter registration campaign that resulted in Macon, Ga., electing the first black sheriff in modern American history.

When Young was elected to Congress. Cooks went along as his chief aide. After Young became U.N. ambassador, Cooks followed him to the U.S. mission there, where, he says, his main job until now has been "interpreting Andy to the staff and vice versa"

"There was a lot of anxiety among the regular foreign service officers thhere about what they were getting into" Cooks recalls. "My job, as the guy who probably understands. Andy's mind best was to make them understand what he was like and what he wanted from them, to find the people that he could work with and to put it all together in an effective team."

on the Caribbean trip, Cooks is operating in similar fashion, acting as the interpreter and go-between for members of Young's entourage. It's Cook who decides what papers go to Young, what gets handled by others and who usually puts the final "O.K." the messages being sent back to Washington.

In many respects, the real odd-man-out of Young's Caribbean team is a woman: Sally Shelton, whose youth and Betty Coed good looks invariably cause people to do a double take when she introduced as a newly appointed Deputy Assistant Secretary of State for Latin American Affairs.

Shelton, 32, finds that a matter for both annoyance and concern. She says heatedly that her appearance should be irrelevant to any consideration of how she can do her job, and she worries about whether her age and sex will be an obstacle in getting the men who dominate the State Department to take her seriously.

"If I were a 32-year-old man, nobody would be paying any special attention to me," she says. "They'd be measuring me on the basis of what I am and what I've done."

That includes studies in international relations at universities ranging from Texas and Missouri to France and Italy, a remarkable fluency in Spanish, French and Italian and a period of teaching political science in Mexican universities.

What took Shelton to Mexico was a brief, unsuccessful marriage to Mexican diplomat. After returning home, she spent six years as an aide to Sen. Llyod Bentsen (D-Tex.) working on Latin American and foreign trade affairs. Early this year, she moved to New York to help manage the international operations of The Continental Group, a major multinational business organization.

Before she could start her new job, however, the White House unexpectedly asked her to become Ambassador to El Salvador. Shelton accepted and then found the offer being yanked out from under her.

An upsurge of terrorism in El Salvador that included the murder of the Foreign Minister caused the State Deparment to have second thoughts about the wisdom of sending a young woman to that Central American country.

Says Shelton philosophically: "I'd say it was about 60 per cent my age and 40 per cent my sex. But anyhow I didn't get the job."

What she got instead was something potentially more important - an appointment as a Deputy Assistant Secretary with responsibility for overseeing U.S. diplomatic activities in Mexico, Central America and the Caribean.