ruby, n.² — Green’s Dictionary of Slang

ruby n.²

[? film star Ruby Keeler (1909–93)]

1. (US black) in pl., the lips, esp. large or full lips.

1942		Pittsburgh Courier (PA) 22 Aug. 7/6: Rubies — (lips).
1961		J.A. Williams Night Song (1962) 125: Let’s go in and wrap our rubies around some cold beer.
1972		B. Rodgers Queens’ Vernacular 174: rubies (camp) lips.

2. (black/camp gay) a man with large, prominent lips.

1972