President Reagan's plans to nominate Justice William H. Rehnquist to lead the Supreme Court as chief justice and to nominate Antonin Scalia to the court are causing many blacks to ask the inevitable: "How will we be affected?"

Answers provided Tuesday night at a reception by the Congressional Black Caucus Foundation ranged from hopeless to gloomy. Most of the Democratic members of Congress there felt the court's delicate balance would shift noticeably to the right although they didn't expect the court to change direction abruptly.

"I'm distressed," Rep. Julian Dixon (D-Calif.) said of Chief Justice Warren Burger's retirement. Because Justice Rehnquist comes from the "far right of the political spectrum," Dixon said, "I am concerned that he would be named chief justice . . . . of the Supreme Court. He has not shown sensitivity to minority people in this country."

Dixon was sorry to see Burger go because he was a known quantity and had occasionally gone against his own conservative philosophy to support a number of legal and social issues including racial desegregation and had delivered landmark school busing and job bias decisions.

By contrast, Rehnquist has favored tuition tax credits for education, which benefit the rich and upper middle class and which some feel seriously threaten the future of the nation's public schools. Moreover, in the Bob Jones case, Rehnquist wanted to establish a precedent by restoring tax-exempt status to a segregated school.

Based on Rehnquist's "peculiar" record in the area of civil rights, a black rightwing publication, "The Lincoln Review," did an odd thing. The publication recently applauded Rehnquist for his "constitutional colorblindness." Of course other people might call it blindness.

Rep. Mary Rose Oakar (D-Ohio) doesn't see colorblindness but "hostility" when she looks at the Rehnquist record. "In the area of civil rights, Rehnquist has been very hostile," she said at the reception. Forget about just blacks, she said, "he has not been a friend of human rights in this country."

According to Rep. Major Owens (D-N.Y.), "The Supreme Court does not move rapidly in any direction, it drifts. But its recent drifts have been alarming."

But there was also a tone of resignation that was repeated throughout the evening like a weary riff. Many black legislators believe that, agency by agency, the Reagan administration is establishing the worst civil rights record in a half century. They complain that the Justice Department, the Civil Rights Commission and the Equal Employment Opportunity Commission have all fallen to ultraconservative Reagan politics.

"We're living in an era when we can't look to the White House for leadership on civil rights or other moral issues such as the right of a woman to have an abortion if she chooses," said Dixon.

But griping about the Reagan juggernaut was not the only refrain repeated throughout the evening. There was also a great deal of praise for the lone black justice of the Supreme Court, Thurgood Marshall. At 77, Marshall, who has had sporadic ailments, is the fourth oldest member of the court.

"We're hoping Thurgood Marshall will hold out a couple more years and that he can be replaced by another Afro-American," said Eugene Jackson, chairman of National Black Network News.

Jackson's concern is well founded. If the Reagan nomination to replace Rehnquist, Judge Scalia of the U.S. Court of Appeals for the District of Columbia, is any indication -- and it is -- Marshall's retirement or the retirement of another justice would open the door for the appointment of a fifth conservative to the Supreme Court and give the Reagan administration a lock on the judicial branch.

As a conservative, Scalia gets high marks for scholarship from liberals and conservatives alike, but his judicial leanings raise some concerns. As Rep. Cardiss Collins (D-Ill.) put it: "The changes spell a lot of trouble for the progressive movement of many groups. We're all likely to be hearing more bad news."

Indeed, the group that may have as much to worry about as blacks is women. Rehnquist staunchly opposed the Roe v. Wade decision as well as other proabortion decisions. A Roman Catholic with nine children, Scalia is personally against abortion.

Now that Reagan's choices are known, there is a single hope that was shared by all of the legislators attending the caucus reception. As Julius Chambers, head of the NAACP Legal Defense & Educational Fund, said: "I hope the Senate carefully reviews both candidates to ensure they have the required judicial temperament and experience." Such hope, unfortunately, seems unlikely to change the scenario the Reagan administration has planned for the Supreme Court.