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Color lives in the memories, as well as the eyes, of the beholder, suggests a German study of how people perceive the color, or colorlessness, of fruit. Karl Gegenfurtner and his colleagues at Justus-Liebig University in Giessen put their subjects in front of a computer screen with digital images of fruits—a banana, for example—in brown, purple or any arbitrary color. The subjects were then instructed to use the computer's software to manipulate the fruits' color. When asked to make a gray—or colorless—banana, all 14 subjects made images that were slightly blue.
“In order for the banana to look a neutral gray, they had to make it bluish,” Gegenfurtner says, “because a gray banana still looked yellow to them.” The actual deviation from neutral gray varied between 4 and 13 percent, but all of them added blue, yellow's complimentary color (the one opposite it on a color wheel) to the images to make them look gray.
But why should our brains distort our perception of color rather than representing it truly? “Our brain uses the knowledge that stop signs and strawberries are red, for example, to recognize them, even when they are barely illuminated by dim moonlight,” Gegenfurtner explains. In effect, the brain adds red to make them recognizable, adjusting their real color toward a “memory color.” The researchers also point out that even in daylight this color adjustment has a purpose. Sunshine contains more blue in the morning, and yellow fruits would shift their appearance toward gray in those conditions. But because of the influence of color memory, bananas appear to have a more consistent hue throughout the day.