It's blue. Very blue. I don't know why it's so blue, but it is. They must have had a meeting about it. They could have made it red, green, maybe a nice shade of orange. Instead they made it blue. It's blue in the caves. It's blue on boats. It's even blue in people's houses. It's all blue. Apart from flashbacks. They're sort of... yellow. Nice flashbacks to happier times when the sun was out and everyone wasn't trying to bite your face off.
The inexplicably successful Underworld franchise just keeps going. Film four is going to be released next year. I mean, proper franchises don't get that many films. There'll probably be a lot of bashing about in caves and unexpectedly complicated backstory. In its defence though, it's blue and has werewolves in it.