Harley Quinn certainly does have that look, as does the new Joker. Makes you wonder if the costume designers just heard “Suicide-something movie” and ran with it without waiting for clarification.
Probably bad lighting and/or post-processing. They’re darker in some of the other copies of the image floating around. (And the original source is David Ayer, so it is an official image.)
From that one shot, I can ID at least $250 worth of buckles on that costume. And I strongly suspect the actual number to be a multiple of that.
No wonder these movies cost so much to make…