Green’s Dictionary of Slang

1. (US) a derog. term describing a black person, esp. light-skinned; often ext. as cocoa-brown.

1928		R. Fisher Walls Of Jericho 269: The plump cocoa porter, his eyes on Shine, clawed absently and futilely at the place on the blanket where his pile should have been.
1931		N. Van Patten ‘Vocab. of the Amer. Negro’ in AS VII:1 27: cocoa-brown. M. n. One of many color distinctions.

2. (US black) of a person, black, with no derog. overtones.

1928

C. McKay Home to Harlem 318: [She] sat [...] with a dapper cocoa-brown youth by her side.