Scientists see what artists always have: colour is illusive

Our perceptual experience is created through an interaction between matter, context and mind

- By Sasha Rakovich

As many people sit at the wheel of their car, they are certain they know what colour is. It's the red traffic light in front of them, the garish yellow hatchback in the next lane, or the green verge banking to their right.

Colour, as many people understand it, is the property of a thing. That light is green. The sky is blue. But scientifically, that's not quite true. No one can experience the exact same colour as you do. Colour is a perceptual experience created by our brains.

It’s the interaction between a material, light and the mind. The way a material absorbs and scatters light affects what reaches our eyes. And colour needs to be processed by the brain.

The shape of objects and the context in which you encounter them can also shape the way you perceive colour. If you've ever picked a paint colour that looked perfect in the shop but turned into something entirely difference once on your walls, you've already encountered this phenomenon.

This notion of colour as experience was recently shown in a study by researchers at the University of California, Berkeley, who used lasers to manipulate participants' eyes into seeing a new colour a blue-green they call olo.

To achieve this, the scientists used lasers to activate specific photoreceptor cells in the retina that detect green wavelengths of light, called M cones. We also have S and L cones, types of photoreceptors that detect short blue and longer red wavelengths of light, respectively. Everyone has slight variations in the number and sensitivity of these cones, so we each experience colour a little differently.