what color are tennis balls

Tennis balls can be virtually any color in recreational play, but at major sporting events, they are fluorescent yellow. The International Tennis Federation (ITF) refers to this distinctive ball color as "optic yellow". However, there is a thin, hazy border between yellow and green, and some people see tennis balls as green, while others see them as yellow. According to a scientist who sampled different parts of a tennis ball in Photoshop, the color of a tennis ball is in between yellow and green, but it skews more towards green than yellow.