It’s a heated debate which has been disputed online this week, as people are on both sides of the fence, are tennis balls green or yellow?

Twitter polls attracting thousands of votes on the surprising issue failed to establish a definitive answer, before Roger Federer finally settled the debate by answering in a cool casual way.

“They’re yellow, right?” responded the smiling Swiss tennis great to the unusual question from an inquisitive father ahead of the Miami Open.

The color has been described as fluorescent yellow, chartreuse, lime green and the fun imaginary composite of ‘gellow’, however the official color for tournament balls is “optic yellow”.

Tennis balls were traditionally black or white, but in 1972 the International Tennis Federation introduced yellow tennis balls after research showed they were more visible to television viewers.

Color expert Andrew Hanson, past chairman of the Color Group of Great Britain and scientists at the National Physical Laboratory, said at the time it’s all to do with how our brains are wired to see color.

“We all have memory colors. We know that bananas are yellow for example,” he explained. “Similarly we know that shadow should be blue. It’s nothing to do with color blindness, it’s all do to with color perception. Essentially it is an illusion but people who see white, are actually seeing white, even though it is not really there.”

Who care what color they are, they’re fun to hit, and opening a new can makes a great sound. I’m ready to play, tennis anyone?