Green’s Dictionary of Slang

(US black) a particularly dark-skinned person.

1918		‘Mademoiselle from Armentiers’ in J.J. Niles Singing Soldiers (1927) 61: I’se glad I is a Buffalo – / ’Cause we is always on de go; / Inky dinky*, parlez-vous. [*The negro sang ‘Inky Dinky’ rather than ‘Hinky Dinky’].
1942		Z.N. Hurston ‘Story in Harlem Sl.’ in Novels and Stories (1995) 1009: Inky dink: very black person.
1970		C. Major Dict. Afro-Amer. Sl. 69: Inky-dinky (loosely used) a negative connotation, sometimes refers to a very dark Afro-American who happens also to be untidy.