Lewis Short
nīgror (noun M) : 1. niger
* Blackness (poet. and in post-Aug. prose): noctis, Pac. ap. Cic. Div. 1, 14, 24; Lucil. ap. Non. 515, 5: mortis,Lucr. 3, 39: nigrorem in ulceribus excitat,Cels. 2, 1: rubidus est rufus, atrore et nigrore multo mixtus,Gell. 2, 26, 14.
Charlton T. Lewis, Charles Short, A Latin Dictionary