ATLANTA (AP) _ A U.S. district judge has ruled that it's possible for blacks to discriminate against other blacks based on the color of their skin.

Judge Charles A. Moye Jr. ruled that race and color are not the same thing.

''It would take an ethnocentric and naive world view to suggest that we can divide Caucasians into many subgroups, but somehow all blacks are part of the same subgroup,'' Moye said. ''There are sharp and distinctive contrasts amongst native black African peoples both in color and in physical characteristics.''

In his ruling Thursday, Moye certified for trial a lawsuit by Tracy Walker of Union City, a clerk typist for the Internal Revenue Service. She contended that her supervisor, Ruby Lewis, ''singled her out for close scrutiny and reprimanded her for many things that were false or insubstantial.''

Ms. Walker's skin was lighter than Ms. Lewis'.

Margaret Fernandez, a spokeswoman for the Equal Employment Opportunity Commission in Washington, said Moye's ruling may be a first.

''If this issue had been raised, everyone here would have been aware of it,'' she said. ''It is unique.''

Ms. Walker's suit said Ms. Lewis considered her to be tardy, lazy and incompetent, and recommended that she be fired. Ms. Walker, who disputed Ms. Lewis' appraisal of her, eventually lost her job.

The defendants in the case - including Ms. Lewis, the Internal Revenue Service and the U.S. Treasury secretary - argued that people of the same race can't discriminate against each other because color has ''generally been interpreted to mean the same thing as race.''

Moye disagreed, citing a Supreme Court ruling that a white employer had discriminated against a naturalized American from Iraq because of his Arabian ancestry.

He said ''there is evidence that Ms. Lewis might have harbored resentful feelings towards white people, and therefore by inference, possibly towards light-skinned black people.''

Ms. Lewis could not be reached for comment Saturday.

No trial date for the lawsuit has been set.