Seeing red, or green

One of the longest-standing philosophical questions is whether we all perceive colour in the same way. A new investigation strongly suggests that by and large we do.

The colour red is often deployed as a warning, presumably because it is the colour of blood – traffic lights or a level crossing being examples. But the possibility remains that one person’s red colour could be another person’s green. Putting subjective conscious experiences into words is notoriously challenging.

In an attempt to gain more insight into the matter, scientists at a Japanese university asked some 700 people to use an eight-point scale to rate the similarity of colour pairs with 93 unique shades that each varied slightly in lightness, saturation and hue. Some third of the participants were colour-blind (mainly red-green) allowing comparison with those with typical colour vision.

The team discovered that, at group level, people with typical colour vision share the same relative colour structure perception as one another. The same was also found for the colour-blind participants, despite them all having differing degrees of red-green colour-blindness. The experiences of red and green were much more closely aligned among the colour-blind individuals suggesting – as we may expect – that they see these colours as more similar than persons with typical colour vision.

The etymology of colour names in the English language takes us back to Proto-Indo-European, a language spoken by a group of people over 4,000 years ago that split off to form a multitude of languages spoken in the West. White comes from ḱweydos, which meant to “shine.” It evolved from the Proto-Germanic hwītaz, and duly entered into Old English as hwīt.