A dark colour often associated with impending judgment or with evil.
Black as descriptive of colour
Mt 5:36 See also Ex 10:15 the plague of locusts; Lev 11:13-14 pp Dt 14:12-13 unclean food; Lev 13:31; Dt 4:11; 1Ki 18:45; Job 28:3; Job 30:28,30; SS 5:11; La 4:7-8 Black horses: Zec 6:2,6; Rev 6:5
Black as the opposite of light
Black in the setting of impending judgment
Black as a symbol of evil