Anthony Burgess, author of A Clockwork Orange
, wrote a fictional biography of Shakespeare called Nothing Like The Sun
, which took this same interpretation of "dark" as its premise: he made the lady an African.
At some point Burgess had been in the military and stationed in a hospital that had a ward devoted to sufferers of advanced syphilis. He was surprised to find that as their minds broke down they started using language in peculiar ways, some of which struck him as poetic. He thought he saw some of the same breakdown of language in the later (crappy) Shakespeare plays, so he worked this into his book, having the bard die of syphilis after having written his last several linguistically degenerated