Union Flag optical illusion is completely mind-boggling

Seeing the world in all its colourful glory is something many of us take for granted. But how different do things look if you're colour blind? In a video created by the BBC back in 1985, an optical illusion featuring the Union flag aimed to educate people on how colour blindness works. And despite the illusion first being shown over 35 years old, it's still completely mind-boggling. 

Originally part of BBC's Horizon programme, the video, tweeted recently, features an image of a yellow and green Union flag with a black dot in the middle. Viewers are asked to stare at the dot for 20 seconds, after which the screen goes white and, due to a "three receptor phenomena" the flag will appear in its original red, white and blue colours. This, as the narrator explains, is due to said phenomena forcing other colour receptors to take over when some "start to tire". 

Almost four decades on, it's fair to say the illusion has captured a whole new audience, with many taking to Twitter to share their amazement. One Twitter user @TheMetamorphUk commented: "That Union Jack trick still freaks me out to this day!". And another, @NicolasBarlow, says: "Brilliant. It definitely works, I was able to see the Union Flag!"

The video goes on to highlight exactly how those with colour blindness see the world, also using the London Underground map design to demonstrate. The footage is not only an eye-opener for those among us who use and rely heavily on colour every day, but offers a wonderful sense of nostalgia to a simpler time that we all need right now. 

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