Was that dress blue or gold? How about that old Vans shoe… turquoise and grey or pink and white?

And now, the latest great debate of our time…

Are tennis balls green or yellow?

This time, however, it’s Roger Federer’s fault.

During a visit to Chicago to prepare for September’s Laver Cup, the world’s top-ranked tennis player was asked the divisive question by a fan.

In a video captured by the fan’s daughter, the man can be heard shouting “Hey Roger! Are tennis balls green or yellow?”

The tennis great flashes a big grin before responding with “They’re yellow, right?”

Little did he know that simple answer would incite a firestorm of debate online.

The short clip was uploaded to Twitter by Delaney Dold, the woman who shot the video, where it has since been viewed more than 315,000 times. In the comments below, Twitter users pronounced their allegiance to team green or team yellow.

There were many commenters who ruled that it didn’t matter what the actual colour of the balls are now that Federer had weighed in on the matter.

Other users provided more specifics for their choice of colour.

Finally, there were some who just couldn’t decide.