Blue has more meanings than any other color on the wheel, ranging from calm and peace, all the way to melancholy, emotional coldness, and sadness. Joy is yellow and light green, because those colors are used to represent happiness, vitality, etc. But this fattie has it backwards. Sad is not associated with the color blue; the color blue is used to portray sadness. There's a semantic distinction there. And a lot of these color theory things are based on science. Our brains respond in certain ways to certain colors. It would probably be a bit confusing for us to see sadness embodied as yellow, or red. I'm sure the Pixar design team did the characters deliberately. They have some of the best animators in the world, and I bet all of them could talk color theory circles around everyone who's criticizing that movie. And besides, the world needs the media to tell kids that being fat turns you into a frumpy sad person.