"A Soul so Black"

Despite the play's title, images of blackness and darkness obsessively pervade Webster's play. These range from conventional imagery (for example, Vittoria's hair being like "the blackbird's feather", hell as being a "black lake", the "withered blackthorn" that is meant to replace the "well-grown yew" in Vittoria's dream [a yew tree that later Monticelso describes as "black and melancholic"], or the descriptions of storm-clouds used to characterize Lodovico -- "thou 'rt a foul black cloud" -- and by Vittoria herself to describe her soul -- "like to a ship in a black storm") to epithets (the coupling of poison and lies as "that black slander", Vittoria's passion described as "her black lust" and a "black concatenation", Gasparo's rage is a "black fury", and the murders of Camillo and Isabella termed "black deed[s]" -- a term used later, also, by Hortensio to describe his suspicions of foul play), as well as costuming (Giovanni's black outfit is described by him as an "imitat[ion] of [Francisco] in virtue") and props (Monticelso's "black-book" of criminals, of which he notes that "Well may the title hold").

Brachiano, in his "distractions", rhetorically asks, "did you ever hear the dusky raven / Chide blackness?" and Flamineo admits that his life, metaphorically, has been "a black charnel". The play concludes with a couplet reinforcing the imagery of murder, lust, and deception as "black deeds", and even on the stage the perceptions of "darkness" would have been visually conveyed through the roles of Zanche, the Moorish serving woman (who, on the Jacobean stage, of course, would have been played by an actor who was neither black nor a woman), and in Francisco's disguise as the exotically named Moor "Mulinassar".

Is the title of Webster's play as much an oxymoron as the titles of the city comedies we have been reading, given the usual connotations of blackness that the term "devil" evokes in early modern literature? If so, why? Or am I merely importing modern imagistic prejudices onto the term "white"?