ATLANTA, JULY 16 -- A federal judge ruled today that a black woman provided insufficient evidence to prove her claim that she was fired from the Internal Revenue Service because of the prejudice of her darker-skinned supervisor.

"The plaintiff has failed to prove by a preponderance of the evidence that she was terminated because of invidious discrimination on the basis of color," U.S. District Judge Charles A. Moye Jr. wrote in his opinion released late Monday.

The ruling was thought to be the first in the nation in a civil discrimination suit filed by one black person against another. Two others, both still pending, have been filed here since testimony ended last February.

Tracy L. Morrow, 27, was fired in March 1986 from her job as an IRS clerk/typist, allegedly for poor attitude and job performance. During the February trial of her civil suit, she said her supervisor, Ruby Lewis harassed her constantly for four months.

Morrow testified that Lewis gave her co-workers preferential treatment and made such remarks to her in private as, "You need some sun," and "You've had life too easy. You're going to have to work for your position under me."

Experts testifying on Morrow's behalf outlined a history within black society of favoritism for lighter-skinned blacks that dates back to slavery.

Lewis, 40, an 18-year IRS employee, denied making the prejudicial statements. She described Walker as an immature, overambitious employee "unable to take no for an answer." Witnesses testifying for Lewis and Morrow described ongoing tension and personality conflicts between the two.

The judge ruled that Morrow's attorneys did not provide convincing evidence that the prejudicial statements were ever made. Lewis "was not wholly innocent" in perpetuating the conflict, but "a personality conflict alone does not establish invidious discrimination," the judge said.

Morrow said later she was surprised the judge found no support for her claim that her firing was in part retaliation for her 1986 complaint about Lewis to an in-house equal employment officer.

Testimony by other IRS employees that Walker was impatient, disrespectful and unmanageable apparently weighed heavily in Judge Moye's decision.

"Plaintiff's working attitude appears to the court to have been the cause for her termination," Judge Moye said.

Michael Weinstock, a Morrow attorney, said he would move for reconsideration of the ruling by the judge on grounds "there are other facts he should have considered."