Green’s Dictionary of Slang

of a black person, light-skinned.

1946		Drake & Cayton Black Metropolis 547: Clothes are both an end in themselves and an adjunct to the social ritual of this café au lait society.
1992		B. Gifford Night People 14: That café au lait gal was in C block.
1999		E. Bunker Mr Blue 323: The second psychiatrist was a café au lait black man.