Although they're brightly-colored now, historically, tennis balls were either black or white. The color depended on the background color of the courts.
The advent of color television changed that, as audiences had a difficult time seeing the ball. Yellow was found to be the most visible color on television, so the International Tennis Federation began allowing the use of yellow balls in 1972.
Ever adhering to tradition, Wimbledon used white balls for several more years, until 1986.
Interestingly, there is some debate today over what people think the true color of today’s tennis balls are. A recent Twitter poll of 30,000 people found that 52 percent think a tennis ball is green, 42 percent call it yellow, and 6 percent selected "other."
Marina Koren picked the story up for The Atlantic and interviewed Bevil Conway, a researcher at the National Institutes of Health who specializes in color perception. She wanted to find a possible explanation for the discrepancy.
Conway explained, “I can think of many more orange or red objects—apples, tomatoes, cherries, most fruit, faces, etc. So it might not be surprising that there is some disagreement about the color of tennis balls."
“They are an odd color, designed to be odd so that they are especially visible on the court. But because they are odd, we haven’t resolved how to label them,” he continued. What do you think? Are tennis balls yellow or green?