If you zoom in really close on the map, it looks like Harley Quinn is red and white. Also since it's named after a DC character I would guess they probably have to give it at least a slight theme in order to get the licensing.
I'm not sure how I feel about Blackbeard's getting a superhero theme but I agree that the Lakefront is going to look great now! I'm looking forward to giving the Joker a try, if nothing else it's unique to the park, and given the park's new commitment to filling dead areas, the park will be in great shape for the future!