In a warm and emotional memorial ceremony, national and local dignitaries gathered in a Northwest Washington church yesterday to eulogize Samuel C. Jackson, 53, a black Republican who served three presidents and carried the banner of civil rights in the high echelons of the GOP.

"What color is love?" asked Bishop Chandler D. Owens of the Churches of God in Christ in his eulogy. "What color is dignity. . . compassion. . . understanding? Sam was not a black man: Sam was a man!"

The gathering was in many ways a unique mixture, 1,200 people in all, black and white, Republican and Democrat. They filled the Temple Church of God in Christ, 1435 Park Rd. NW, to overflowing. Jackson's heavy brown and gold casket, covered by a big American flag, rested up front under the speaker's podium.

Washington Mayor Marion Barry and national civil rights leaders sat side-by-side with U.S. Sen. Robert Dole (R-Kan.), black religious leaders, and a heavy sprinkling of white lawyers from Jackson's New York law firm, Stroock & Stroock & Lavan.

A cabinet member -- Samuel Pierce of HUD--was there, and Arthur A. Fletcher, formerly assistant secretary of labor in the Nixon administration, arrived bearing personal messages from President Ronald Reagan and Vice President George Bush.

Reagan's message praised Jackson's strength of character and declared: "His work will leave a lasting mark on our society." Bush's message called Jackson "a fighter for the right" and went on to note that "as a black Republican, he all too often had to lead a lonely charge."

Jackson moved to Washington in 1965 to become one of the five original commissioners of the U.S. Equal Employment Opportunity Commission in the Johnson administration.

In 1969, President Nixon named Jackson assistant secretary of Housing and Urban Development for metropolitan development, the third-ranking official in the department.

In January, 1981, Reagan had named Jackson to the Blue Ribbon Commission on Housing. As a District of Columbia delegate to the 1980 Republican National Convention, Jackson worked for Bush's nomination.

Yesterday, many old friends eulogized Jackson. They described him as a religious man, a brilliant attorney, and a person with a good sense of humor who lived intensely, as if he realized how short his life would be.

Jackson died of cancer Monday. Before he died, he had himself planned yesterday's ceremony, choosing the hymns and the speakers.

"Sam had a great influence on my actions and my life," said Dole, who knew Jackson long ago in Kansas, where Jackson grew up. "He was always an optimist, and to be a Republican you really had to be an optimist."

Barry called Jackson "a river of compassion. . . a river of courage."

The Rev. Benjamin Hooks, executive director of the National Association for the Advancement of Colored People, said Jackson had adhered to the principle that America could be nothing unless it was fair to everyone. He said Jackson had made sacrifices "for us and for black people throughout this country."

The Rev. Jerry A. Moore Jr., a Republican member of the D.C. City Council, was one of many speakers who characterized the memorial service as more a celebration than a sad occasion. "We are a stronger people today and more noble because of Sam," he said. "I'm glad I lived in the age when Sam Jackson lived. He is the foundation where I stand politically."

U.S. Del. Walter Fauntroy of Washington and Rep. Parren Mitchell of Maryland, both Democrats, were there. Vernon Jordan, former head of the National Urban League, was in the audience.

At the end, Bishop Owens declared, "Sam, you fought a good fight!" and the choir, clapping, sang "Oh when the saints go marching in" and the casket, followed by the weeping family and the congregation, was taken out on its way to Kansas, where there will be a funeral and burial.