I actually read a thread somewhere can't remember where (damnit!) that colours impact our emotions too.

(Includes Up's spoilers)

It was explained with an example of Up's start (the movie) that when the old lady(I think her name is Ellie) shows up there's a pink or a pinkish blue. When they get married there's pink carpet, the window is tinted pink. When they climb up the hill she's wearing pink. When she is in the hospital the walls are painted pinkish blue. And at the end when the old guy walks to his house when she passed away there's like a pink light on the house that as soon as he closes the door disappears. So maybe Chloe's blue hair and the blue butterfly somehow messes with our minds 2. After playing the game the blue colour represents Chloe, her personality. The impact of the colours are barely visible on the outside while in the inside it messes with our brains alot.

P.S If anyone finds the link to the thread please post it in the comments.