Green’s Dictionary of Slang

1. (US) a black person.

1941		C.S. Johnson Growing Up in the Black Belt 259: Black youth are called by such derisive names as ‘Snow,’ ‘Gold Dust Boys,’ ‘Blue Gums,’ ‘Midnight,’ ‘Shadow,’ ‘Haint,’ ‘Dusty,’ ‘Polish,’ and ‘Shine.’.
1993		B. Moore Lex. of Cadet Lang. 233: midnight a negro; any very dark-skinned person.
2001		(con. 1981) A. Wheatle East of Acre Lane 110: Give us a fucking name [...] A fucking name, Midnight!

2. (US black) a particularly dark-complexioned black person.

1972		D. Claerbaut Black Jargon in White America 72: midnight n. a black person whose skin color is very dark.
1980		E. Folb Runnin’ Down Some Lines 30: Expressions like coal bin, black bird, midnight, midnight the cat [...] are used both playfully and pointedly to characterize extreme blackness.