Color is one of the most powerful tools you'll use as a filmmaker.
How do you tell a story? If you're a filmmaker you know that you have so much more than the written word at your disposal. You have dialogue, camera movement, framing, costuming, set design, and editing all there waiting to inform and entertain your audience. But there is one very powerful narrative element that should never go unnoticed on any film production: color.
Caldeano does a great job of breaking down basic color theory for those who may not know much about it, but he also brings up a great point for those who may have more experience working with color with their films. It's something that seems pretty simple but it actually goes unnoticed rather easily in the chaos of film production.
Even though color tends to have an inherent emotional and psychological "meaning" or effect, you as a filmmaker have the power to define what different colors represent in your own work. For example, though white may represent purity and innocence for most, you can redefine it in your film to mean the exact opposite—corruption and defilement.
One example of this is in M. Night Shyamalan's The Sixth Sense. The color red is famously used in the film not to symbolize passion, love, or lust, but, as the director says, "anything in the real world that has been tainted by the other world." Another example is Gary Ross' Pleasantville, in which color itself, which one might expect to symbolize vibrancy and life, is used to represent a rebellion against the austere way of life of a black and white society.
So the next time you're planning a film, take some time not only to consider which colors would benefit your story, but which ones you'd like to redefine as a filmmaker.