One of the users shared a photo of a trainer and asked members to tell her whether they thought the shoe was blue and grey or pink and white.
She said: “My friend has just sent me this asking what colour the shoe is, I would say pale pink and white, but she insists its pale blue and grey.”
When she opened it up to the floor, comments flooded the thread.
Within the space of an hour, the post had gained 1,000 comments and caused a serious debate.
Then someone took the debate to Twitter.
It appears most believe the trainer is blue and grey, but a significant number swear it’s pink and white.
Some are claiming they can see both.
If you’re too confused to make up your mind, maybe follow this Twitter user’s suggestion.
If the debate between your friends is getting too heated we’ve found the one true answer.
HuffPost UK reporter Jessica Pitocchi solved the mystery with a bit of online shopping: