At this point in history, color theory has established a well-documented dialogue. Various studies of human psychology note that the color yellow may elicit feelings of comfort, while red tends to make people hungry or impulsive. Marketing experts refer to the pairing of red and yellow as the Ketchup and Mustard Theory. Green and earthy tones are sometimes used to convey a message of healthiness and environmental responsibility.

One might feel moody looking at the ocean's deep blues or soothed by the clear blues in the sky. How does one decide how much blue to imbue? The visual artist must...