The color of the negative space in a crossword... or a hint to the rebus in
13A13AExperimental rock band named for an obscure electronic music genre
[-----] ,
39A39APost-punk band formerly fronted by Isaac Wood, who left in 2022
[---------------] ,
13D13DRock band often credited with inventing heavy metal
[--------] , and
39D39DPost-industrial duo comprised of Ada Rook and Devi McCallion
[--------] ?