What is the reason for the violation of wearing black underwear, why tennis matches should wear white

Beijing time on July 13, 2017, the 2017 Wimbledon continues, in the first round of the junior men's doubles match appeared an embarrassing scene, China's young Wu Yi Bing and his partner Pilos because of the black underwear does not conform to Wimbledon's tradition of all-white, the referee asked to go off the court to change. Wimbledon since its inception, the tournament has strictly required players to dress in white, intended to express respect for the British royal family, and in 2014 even issued a more stringent dress code, before the game to the players issued a Wimbledon "white ten" dress guide, detailing the rules, including the game process to see the underwear must be The first time I saw the game, I saw the game, I saw the game, I saw the game.