Arabic

saḥar- - whiteness overspreading blackness (Lane 1317)

PWS
*šḥr - to be white on black or black on white (Kogan 2005c:191)

May be tentatively compared to Akk. šūru, šuḫru if the latter indeed denotes dark color as suggested in AHw. 1287 (Bulakh 2003: 13–15; Bulakh 2006: 195–196).