Did you know that when one percieves the green colour, no matter how purely green the subject is, the red and green cones are also stimulated to some extent? That's because green sits in the middle of the visible spectrum and its frequency response overlaps the other two colours and hence the green we see isn't a pure green. Now, scientists have figured out a way to stimulate just the green cones, allowing the subject to perceive a pure green which apparently looks very different to what you'd expect, which they call olo. Heck, I'd just call it hypergreen! Sounds so much cooler.
This turquoise square is the closest we can get to it with regular colours and you can see that it's basically green.

www.theguardian.com
Here's another way to see an impossible colour, bluish-yellow, and this experiment you can do at home:
nerdzone.uk
This turquoise square is the closest we can get to it with regular colours and you can see that it's basically green.

The bold – and contested – assertion follows an experiment in which researchers in the US had laser pulses fired into their eyes. By stimulating individual cells in the retina, the laser pushed their perception beyond its natural limits, they say.
Their description of the colour is not too arresting – the five people who have seen it call it blue-green – but that, they say, does not fully capture the richness of the experience.
“We predicted from the beginning that it would look like an unprecedented colour signal but we didn’t know what the brain would do with it,” said Ren Ng, an electrical engineer at the University of California, Berkeley. “It was jaw-dropping. It’s incredibly saturated.”

Hue new? Scientists claim to have found colour no one has seen before
Contested discovery achieved by experiment firing laser pulses into eyes, stimulating retina cells
Here's another way to see an impossible colour, bluish-yellow, and this experiment you can do at home:
Blueish-yellow: the forbidden colour
Another great video from this fascinating channel, The Action Lab, where the presenter demonstrates physical phenomena with home experiments. While you can't actually create a genuine blueish-yellow, it's possible to trick your brain into seeing it, sort of. I've done it and it looks really...
