And it involves four colours: black and blue, and white and gold.

A Tumblr user, under the name "swiked", posted a photo of a dress and asked her followers for help. But it was not fashion advice she was after.

"Guys please help me," she wrote.

"Is this dress white and gold, or blue and black? Me and my friends can't agree and we are freaking the f--- out."

The conundrum has since gone viral, confusing and dividing social media users far and wide.