“Five people have been able to perceive a colour never before seen by human eyes, after researchers used lasers and tracking technology to selectively activate certain cells in their retinas. The blue-greenish hue has an intensity, or ‘saturation’, outside the natural range of colours seen by humans.

The work is ‘amazing technically’ and an ‘extraordinary achievement’, says Kimberly Jameson, a colour-vision scientist at the University of California, Irvine.

This is not the first time researchers have stimulated individual cone cells — the photoreceptors in the eye whose signals the brain interprets as colour. But this time it was done across an area large enough to alter a person’s vision substantially. ‘What is novel in this study is the evidence that such new colours can, in fact, be perceived,’ says Sérgio Nascimento, a physicist specializing in human vision at the University of Minho in Braga, Portugal.”

From Nature.