The ribbons may be black, red or green, but whatever the color they are being worn by black Americans around the county as symbol for the special horror and sense of helplessness they feel about the unsolved killings of 20 black children in Atlanta.

Cooks frying fish behind the counter of Morgan's Crab House on Georgia Avenue in Northwest Washington wear them. So do little boys in the first grade at the Immaculate Conception elementary school in the heart of Washington's central city ghetto.

The ribbons were worn by black and white students this week at Alexandria's George Washington Junior High School. The ribbons were the emblem for the mostly black crowd of 1,000 who marched through the streets of Chattanooga a week ago chanting, "We want it stopped."

And they were the emblem for the 1,800 who poured into the offices of radio station WOL here last Saturday during an all-day radiothon to raise public consciousness about the slayings, and for thousands of others who have attended church services or other observances.

The mysterious Atlanta killings have been a tragedy for the nation, but they have caused special agony for back Americans in a way that once again illustrates the differing perceptions of two societies, one black, one white, that the Kerner Commission talked about nearly 14 years ago.

Atlanta police say they have no real clues about the killer or killers, nothing to indicate that the murders were racially motivated. for many whites, the case seems to be yet another gory occurrence with clear parallels in the Son of Sam murders in New York and the Zebra killings in San Francisco.

But, for many blacks, the Atlanta killings summon up quite different feelings, racial feelings. Anxiety. Fear. Suspicion. Confusion.

Listen to James Teule, 30, a construction laborer of Northeast Washington who talked about the murders the other day while he stood in line at Morgan's Crab House:

"Atlanta is very disturbing. It's constantly on my mind, to the point of sleepless nights. The problem is understanding lynching and similar kinds of racial violence in history. In none of these cases has the federal government come to our aid.

"I don't think it's a sick person [who is responsible for the murders in Atlanta]. I think it's organized. The blatant racism that we suffer in America is just another level of the killing of black children in Atlanta."

Teule is reminded of political realities, too. "Ronald Reagan himself," he added, "is a sign of that racism -- his whole diversion of funds from social programs to the military budget.

"I don't think Reagan has any concern in seeing that racial violence be stopped. Take his statement that he never knmew about problems of race [when growing up]. That's absurd."

Youths on the streets of Washington may not have learned much history in school, but they can tell you about the era of post-Reconstruction after the Civil War, when the clock was turned back on emancipated blacks.

Those blacks who have studied American history remember the presidency of Woodrow Wilson not only for his "Fourteen Points," but also because it was a time when many blacks were booted out of positions in the federal civil service.

So, when many blacks talk about the Atlanta murders these days, they talk about them in the context of other contemporary events: the bold reemergence of the Ku Klux Klan, the killings of black men in Atlanta, Buffalo, Salt Lake City and towns in the Midwest, the new political assaults on affirmative-action programs, busing legislation and President Reagan's cuts in Great Society programs.

And there is pique among blacks about a feeling that white Americans who got so concerned about fate of American hostages in Iran seem to regard the Atlanta killings as just another crime story in the newspapers.

"At least symbolically -- and it's hard to think of 20 deaths as being symbols --- [the Atlanta murders] appear to blacks to be a finale of a range of regressive policies of an uncaring government and an uncaring white public," said Bob Woodson, a black scholar who is a resident fellow at the right-of-center American Enterprise Institute.

Morris Morgan, owner of the Georgia Avenue crab house, said, "If you look at the way the elction turned out, that gives you, as the old folks say, the handwriting on the wall. . . . Since the election, a lot of blacks feel they're on the outside looking in and it's not going to get any better.

"The kids want to work, but when it gets to the point that they're going to cut out Ceta [Comprehensive Education and Training Act], you can feel the frustration of the younsters," he said. "We are definitely going backwards. We are not progressing at all."

What has been significant about the sudden appearance of the red, black and green ribbons is that they blossomed nationwide without any organized effort by civil rights groups or elected officials. the gesture is a spontaneous response from the people.

Reporters who have looked into the matter trace the idea back to an elderly back women in Philadelphia who suggested it as a way to bring the same kind of national attention and sense of urgency to the Atlanta murders that yellow bows had symbolized for the hostages in Iran.

Here, the commemoration has been picked up by radio station WOL, by shopkeepers and by men like John Watson, owner of the 7-eleven store at Georgia Avenue and Piney Branch Road, who not only hands out the ribbons at his store but has persuaded the 19 other 7-eleven owners in this city to distribute them.

"I have kids. I have a young daughter," said Watson, who is black. "I can't understand what these parents are going through.

"There are a lot of people who want to express their feelings about this tragedy. . . . they feel the more attention that's focused on this tragedy, the more likely there'll be a quick response."

Columnists and editorials took turns last week beating up on Washington Mayor Marion Barry for saying he believes there is a mood in the country that condones attacks on blacks and that he feels the federalk government would have put forthe greater effort had the victims been white.

The columnists seemed to feel that Barry's comments could whip up hysteria at a time when calm heads are needed, a criticism that misses a more significant point: what the mayor had to say the other day was a good deal milder than what many blacks have been saying for weeks in living rooms and on street corners, in barbershops and on the bus. His remarks seemed temperate compared with the emotions of black citizens generally.

They do not quote the sayings of the mayor up at Morgan's Crab House these days. They are far more likely to be heard talking about the sayings of Malcolm -- the late Malcolm X, that is.

Teule, the construction laborer, dismisses black officeholders, whether here or in Atlanta, as not being particularly relevant to the problems at hand. Black figureheads, he calls them.

"With all the black officials we've elected around the country, I don't feel that's done us any good," he said. "I think they tend to be more concerned about their paycheck. We have all these elected officials, and we stil have unemployment, we still have an inferior educational system."

Turn on one of the soul radio stations here these days and you are likley to hear the firm, stern voice of the late Malcolm X. Teule is listening.

"Malcolm told us that our first line of defense is since no one else is going to give us protection," he said. "I'm not talking about indiscriminate retaliation. I'm talking about stopping those poeple who're doing [the killings]."