The source material also suggests that Deadpool suffers from mental disorders as a side-effect of his extreme healing abilities. These include: attention deficit hyperactive disorder, manic-depressive disorder and onset schizophrenia.
Harley's skin turned into a white-blue color from jumping into chemicals. The chemicals turned her skin a different color, which is why her skin looks kind of like the same color as the Jokers. Although, there are several versions of Harley Quinn and the Joker, so this may not be 100% accurate.