Cast your mind back, if you can, to the simpler days of 2015.

It was a time when all of our troubles seemed so far away, and debate over a dress that was black and blue - or white and gold, depending on who you asked - became an obsession for about a week. It seemed simple enough at first: the dress certainly looked blue, but more and more people insisted it was actually white.

Even a photograph of the dress hanging in a store couldn't settle the raging argument, and people came up with some far-fetched explanations about why the disagreement began in the first place. Was it a magic photo? Was someone secretly editing the picture to trick us?

A new viral image has brought that argument bubbling back to the surface, and if you still argue with family members about "the dress" to this day, expect to have strong feelings about "the shoe."

The question is simple yet devious: is this Vans sneaker grey with teal laces, or pink with white laces? The answer might surprise you, and we promise there is an answer.

The reason for the confusion about this photo is the same as the original dress picture, but there's a new clue hiding in this photo.

Notice the shoe's owner looks a little green under the gills? This is evidence that the photo has been color corrected. Combined with the washed-out look of a camera flash, the shoes "change color" in the new photo. Twitter user @dolansmalik has helpfully corrected the photo to show the real colors.

So that settles that. While the shoe is definitely pink (and the dress was definitely blue), the photo has been manipulated to make it seem green and grey. That's why some people answer differently: sharp-eyed folks can tell that the colors in the photo are really a muted pink, because they know instinctively that the hand should be a rosy color too.

Here's a better demonstration of this "trickery" at work:

There's no red in this photo, just different shades of light blue. But your brain adjusts to make the photo seem "more red," because of a trait called "color constancy" that balances out your field of vision. It's the same reason colors seem to "shift" a bit when you step outside the house, under a bright blue sky.

Just like the hand, your brain knows that the strawberries should be red, so it adjusts their color the most. Confused yet? So are we! But at least we can say for sure that the shoes are pink.

Share these pictures with your friends to boggle their minds!

[H/T: Mashable]