Green blood is one of the most unusual characteristics in the animal kingdom, but it’s the hallmark of a group of lizards in New Guinea. The muscles, bones and tongues of these lizards appear bright, lime-green due to high levels of biliverdin, or a green bile pigment, which is toxic and causes jaundice. Surprisingly, these lizards remain healthy with levels of green bile that are 40 times higher than the lethal concentration in humans.