The color of a tennis ball is a subject of debate, but the official color of tennis balls used in professional competition is yellow, according to the International Tennis Federation (ITF) . However, some people perceive tennis balls as green, and this may be due to factors such as lighting conditions and how our brains perceive colors. Some scientists hypothesize that people who discount cool colors see tennis balls as yellow, while those who discount warm colors see them as green. It is worth noting that tennis balls can be any color, and in recreational play, they can be virtually any color, including green, purple, and pink.