I see the shoes (pictured) as mint green and grey, but a friend sees pink and white. Is this due to differences in our brains? Are we continually seeing different versions of the colours around us?
Raymond Green, Kingussie, Highland, UK
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My wife sees this shoe as pink and white while holding the magazine close up. However, by experimenting, we have found that from exactly 2.4 metres away, she sees it as green and grey. The change of colour is quite sudden. I see it as green and grey at whatever distance. We have never noticed any other differences in colour perception apart from 鈥渢hat dress鈥� a couple of years ago.
Editor鈥檚 note: 鈥淭hat dress鈥� is a photograph of a dress that went viral in 2015, which some people saw as blue and black and others as white and gold.
Hazel Beneke, Banksia Beach, Queensland, Australia
The letter writer鈥檚 friend may have a form of colour blindness called deuteranopia, due to a lack of retinal receptors for green. My husband had this condition and often described grey clothes as pink, and vice versa. His brain learned to compensate, and this allowed him to see red berries and flowers on green bushes if viewed under artificial lighting.
Julian Money-Kyrle, Calne, Wiltshire, UK
Unless one of them is colour-blind, I would expect two people to agree on the shoes鈥� colour if they saw them in the flesh. The issue is determining the actual colours from a photo. This process doesn鈥檛 work well when we are looking at photographic prints, where the colours reflected by the ink depend on whether the lighting is continuous-spectrum (such as daylight and halogen light) or has spikes at specific wavelengths (such as fluorescent and LED light).
This can result in the phenomenon of metamerism, with colours matching under some lighting conditions and not others. For example, the enamel finish on a cooker I once bought matched the rest of the stove under daylight, but was noticeably greyer with the kitchen lights on.
However, there is a clue in this photo: the hand holding the shoe. The skin is roughly the same shade as the main body of the shoe itself, so unless the hand belongs to a corpse, I would say that the shoe is in fact pink and white.
James Stone, University of Sheffield, UK
The perceived colour of an object isn鈥檛 a property of that object. It is an estimate made by the brain that it attributes to the object.
The brain has to make an educated guess about the true colour of any given item based on clues in the local environment. For example, if an object is viewed under red light, then most of the light reflected from it is red, but the colour of the object is usually perceived correctly. I say usually because physically accurate perception depends on the brain knowing that the item is being viewed under red light, so that the effect of that red 鈥渨ash鈥� can be taken into account.
Consequently, when an object is viewed with little lighting context, as with this picture of a shoe, the brain has to fall back on its default assumption of the illumination.
鈥淭he brain has to make an educated guess about the true colour of any given item based on clues in the local environment鈥�
The difference in observations of the shoe鈥檚 colour suggests that the brain鈥檚 default assumption for some people is that the illuminant is slightly red, and hence they see the shoe as white and pink. Others assume that the illuminant is slightly green, so perceive the shoe as green and grey-ish.
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