This is something that's so simple once you take time to understand it. People have studied colors for perhaps thousands of years. Colors evoke certain emotional and physical reactions in people, and we’ve only begun to understand this.
As a consumer, it’s really cool to understand why you're inclined to feel a certain way about a certain store or brand.
And as a business, this phenomenon can be used to create an identity for your brand, or portray emotions that you want your customers to feel. By incorporating a certain color in your logo, or plastering specific colors on your advertising campaign, you can create a simpler association for your customer to understand, based primarily on the emotions evoked by those colors.This can also do wonders when optimizing your Facebook profile, as well as your Twitter profile.
While this article focuses on color psychology as a whole, and uses logos and brands as main examples, you can extend this to more specific areas of marketing.