Yes this is old as hell, but nobody brought it up yet, so I may as well.
So I was looking for a good read in aiga, and I found a title which caught my attention that stated " Red and Yellow Kills a Fellow ". First, I lol'd because I assumed they actually thought those two colors can kill a person. So I looked more on it and find it very interesting.
LINX:
Red and Yellow Kills a Fellow: Voice: AIGA Journal of Design: Writing: AIGA
So they are basically saying the two colors combined ( red and yellow ) make us want to eat more, it sounds a bit ridiculous but read the entire thing to learn more- based on the examples they stated it makes you wonder, A LOT. I mean McDonalds? Wendies?!? CHECKERS?!?? Look at checkers website ( google it ), think about all those places that you ate at. Apparently, red alerts you and distracts you, and yellow really does make you "mellow", weird how the both combined is hunger too.