Color is part of humanity's language, a way to understand visually. It's been important to culture, and has been integrated many times in art, design, and even photography.
Color harmony plays a huge role in delivering messages -- and it's important that the artist is careful enough to use them. It's not the first thing we would pay attention to when composing images, but from the audience's point of view, it's the loudest cry. Moods are created, aesthetics are defined, the psychological impact is being delivered.
In this video by Mango Street, they define the importance of picking your palette, whether you're a designer, painter, or photographer, and the breaking down of several techniques to improve your chromatic language.
Preview image was taken from the video.