The photograph shows a group of young girls wearing seemingly different-colored T-shirts as they smile for the camera with a tortoise.

a group of people sitting posing for the camera: A mind-boggling optical illusion has divided the internet after appearing to show a black-and-white picture of school girls in colour© Provided by Associated Newspapers Limited A mind-boggling optical illusion has divided the internet after appearing to show a black-and-white picture of school girls in colour

Why do we see color in a black-and-white snap?

Upon closer inspection, one can see that the students are actually covered in streaks of red, blue, yellow, orange and green lines. The brain is tricked into filling in the blanks with the mind, giving the illusion of solid colors where there are none.

‘This is a black and white photograph,’ Twitter user Lionel Page, from Sydney, said.

The snapshot is said to trick the brain into filling the blanks with the mind, giving an illusion of solid colours to appear where there are none© Provided by Associated Newspapers Limited The snapshot is said to trick the brain into filling the blanks with the mind, giving an illusion of solid colours to appear where there are none

‘Only the lines have color. What you “see” is what your brain predicts the reality to be, given the imperfect information it gets.’

The picture was originally taken by Chuwa Francis but was later edited with a ‘color illusion remix’ by Øyvind Kolås.

‘The image for the post is a visual/artistic experiment playing with simultaneous contrast resulting from other experiments these days,’ the post said. ‘An over-saturated colored grid overlaid on a grayscale image causes the grayscale cells to be perceived as having color.’

The image has been retweeted more than 14,000 times on Twitter, and has since been doing the rounds online, including on Reddit.

‘For me, the green and blue lines work the best and seamlessly blend into the background,’ one commenter said.

Another said: ‘Red looks like a grid on a grey background.’

One explained: ‘I think it’s because the contrast between the red and dark colored shirt is greater than that of any other color combination in the picture. I know the human eye can see more shades of green than any other color, but I’d imagine we see red more quickly because it implies danger (same color as blood).’

Many people suggesting ‘squinting’ your eyes to see full colors.

‘Try squinting your eyes it goes full color its kinda crazy how much your brain fills in,’ one person suggested.

Another said: ‘Squint or cross your eyes a little and the whole picture becomes color. It’s brilliant and makes me want to rock up and down in a corner crying all at the same time.’

Meanwhile, some people said they didn’t see any illusion besides the black-and-white image with lines overlayed.

‘What I see is a black and white photograph with colored criss-crossed lines overlayed. This isn’t an optical illusion for me at all. Nothing special here,’ one said.

And another commented: ‘I only see a black & white photo with colored lines. What am I missing?’