Graphic design training includes at least one foundation course in Color and Design. You learn all the nuances of color and how it works - and doesn't - to catch the eye, hold attention, and convey an impression without a single word. There's work with the visible spectrum in both pigment and light. There's study of color temperatures, psychology of color, complements and hues plus much more. These days, a good instructor may even throw in a bit of cultural color training so one can intelligently design products for a global market.
To get a sense of how color and branding go together like PB&J, check out this post that includes a visual diagram of the world's most powerful brand marks and logos. You'll see what I mean.
kiss my black ads: The Most Powerful Colors in the World