synesthesia 1 : a concomitant sensation; especially : a subjective sensation or image of a sense (as of color) other than the one (as of sound) being stimulated 2 : the condition marked by the experience of such sensations
chromesthesia : synesthesia in which color is perceived in response to stimuli (such as words or numbers) that contain no element of color
People with synesthesia experience things differently. They might, for example, experience a bitter flavor when they see yarn. Chromesthesia (also referred to as chromatism or color hearing) is a particular kind of synesthesia in which one perceives color in response to stimuli, for instance perceiving the color red in response to the number 5. The esthesia in this pair of words is modeled on the second part of anesthesia, a word that traces back to the Greek anaisthēsia, meaning "insensibility," which in turn is from a- ("not") and aisthēsis, meaning "perception."
Her letter chromesthesia is especially strong, and if a word begins with a "red" letter, for example, its redness may spread to involve the whole word.
— Oliver Sacks, Musicophilia, 2008
Tesla, a pioneer in the field of electricity, could discern the flavor of certain sights; looking at small squares of paper in a dish of liquid would fill his mouth with a horrible taste. And so on. Synesthesia, a recognized phenomenon for the last three hundred years or so, enjoyed a special vogue in the late nineteenth century among spiritualistically inclined artists. Today about one person in two thousand is gifted—or cursed—with sensory crossover….
— Jim Holt, Lingua Franca, September 2001
What is it like to have synesthesia? According to one woman with "color hearing," "It's like a special gift most of the time—almost any music to me is like the opening scenes of Fantasia or a laser-light show. The minus side is that sound is very distracting when I'm trying to work, because I can't 'turn off.' And most piped-in music drives me crazy; it tends to look like grandmotherly dresses—little pattern prints in dull grey."
— Vogue, November 1985