Relative newcomer Jess Weixler stars in an upcoming movie called Teeth about... well, there's no easy way to say this, so I'll put it simply: Her character's genitals have teeth. Her crotch is a Venus Flytrap, and it is no vegetarian.
Given that, maybe this all makes sense.
Maybe if one of us had to be associated forever with having little shop of horrors in our pants, we'd ALSO shave half the skirt off a Disney Pretty Princess costume and layer it like body armor over a black skirt. Maybe we'd WANT to distract from being The Pretty, Pretty Face Of Vagina Dentata by borrowing a color scheme from a particularly nasty bruise. Honestly, no one knows what the appropriate reaction is, because no one else has ever been faced with being so closely identified with an angry lady-maw.
Well, except for Disney, since I just dragged them into this. If Minnie Mouse starts wandering around Burbank in something similar, we'll be well on our way to a new, groundbreaking understanding. Also, we'll put in a warning call to her gyno.