A pity they hadn't read Gene Wolf's _Book of the New Sun_ in which the main character wears robes of "the hue fuligin, which is darker than black, admirably erases all folds, bunchings and gatherings so far as the eye is concerned, showing only a featureless dark."[1] From the Latin for soot.[0]

[0] https://www.merriam-webster.com/dictionary/fuliginous

[1] http://www.technovelgy.com/ct/content.asp?Bnum=1495