Colors convey strong emotional meaning to an audience. Marketing research studies have been done regarding the subconscious perception of color and its ability to drive consumer behavior.
Red, yellow and green have been shown to increase hunger and impulse purchases, which is why we see this combination frequently used by fast food chains and manufacturers of junk food items in retail packaging.
Blue is seen as reliable, conservative and dependable. Used frequently by financial institutions and insurance companies.
Green is associated with freshness, growth and renewal. Used frequently to convey organic products.
Grey conveys a sense of refinement and sophistication. Often used in the advertisement of luxury items.