You don’t always consider it when you watch movies, but you are being manipulated by color. Think about Wes Anderson’s pastel films, or the vibrant tropical birds in nature documentaries. The real world certainly doesn’t look that way. That’s because for every film there’s a colorist behind the scenes, controlling the hues in each shot. And they’re not just trying to make the footage look pretty—they’re also using color to influence what we think and feel. Here’s how it works.

In a political ad, scenes of a candidate’s opponent have a dark blue tint, which is seen as negative and distant.

Colorists’ main job is to make film footage fit with what we’d expect to see in the real world. If they’re editing a scene of a woman walking down a street in daylight, the brightness and hues need to be consistent in each shot because that’s what our brains anticipate. But beyond those standard fixes, colorists have a sort of “rulebook of emotions” they use to convey feelings in a scene, says Dave Markun, a colorist who has worked in film and TV for four decades. (Credits include Nova and Nature documentaries and the National Geographic Explorer TV series.) For example, he says that warmer colors like yellow are inviting and friendly, whereas blues are considered more negative and distant. So if you pay close attention to, say, a political ad, you’ll notice that scenes of the candidate and her family have a yellow tone while a scene of her opponent has more of a dark blue tint. That’s the colorist’s subtle influence on your emotions.

The same approach applies to other hues: colorists add red to suggest strong emotions, like anger or passion or love—it tells the audience to pay attention. Red’s close cousins, magenta and purple, are the unicorns of film. They tend to be applied to something unusual, Markun says, because they’re such noticeable, atypical colors.

And when a colorist wants to express creepiness or disgust, he’ll pick fluorescent green (think: The Matrix). “When you see green at night, it’s a disturbing color,” Markun says. “Nothing looks normal or beautiful.” Weirdly enough, colorists also use green to make a scene look normal. When we see green where we normally expect it, like a lush green lawn, it conveys happiness and health. “If I want to create a somber scene, the first thing I do is desaturate the green,” Markun says. “It takes the happy connotations out of a scene because it indicates that things are dry and diseased.”

The Matrix Warner Brothers

Colorists can even express more abstract concepts through their work, like going back in time. To show a past event, they add contrast and desaturate the scene, and everyone recognizes it as a flashback. “It distances the viewer from reality,” Markun says. “It tells them that we’re watching something we’ve seen before, like a childhood memory.” The technique also works to convey a dream sequence.