Your color, choose a side

When you see the color red, what do you think of?
Love? Roses? Blood?
What about blue?
Sadness? Blue? Water?

Why do we associate colors with emotions or objects immediately?

Our minds try to find reason, truth, and when it does it feels good, content.

We use such associations for colors in design to convey emotions, or perhaps trigger memories of a place, person, or thing. This is a psychological compensation called "color constancy" where we think that grass must be green and the sky must be blue.

In the comic book world, colors are used to help "determine your side"- Hero or Villain.

An excellent use of the color spectrum, combined with facial expressions can be seen in DC's "Green Lantern" series:

BlackestNight: Tales by `Bakanekonei on deviantART

In this case, the colors of the person (and subsequent corps) reflect an emotion:
"In DC Comics, the emotional spectrum is divided into the seven colors of the rainbow, with each color corresponding to a different emotion:
rage (red),
avarice (orange),
fear (yellow),
willpower (green),
hope (blue),
compassion (indigo),
and love (violet)." (http://en.wikipedia.org/wiki/Emotional_spectrum)

The "warm" colors are considered the villains and the "cool" colors are "heroes". Green is the "middle ground" though in general is a "hero" group.

Why is this?

I think it is because warm colors have a kind of "life" in them, they excite our eye, give off a kind of "energy", where as "cool" colors try to calm us, they "bring us down" instead of "excite" us. In this sense, the colors tied with their respective emotion is based on this, and our already conceived view of that color. Though yellow if we think about it, usually represents happiness, or the sun, but in WWI, it represented fear and death (the mustard "yellow" gas) and also represents sickness (decay, like in rotting teeth). It is in this context that we must be careful to choose our colors wisely, and use them alongside the context from where they are placed to communicate through design properly.