Horizon: Do You See What I See? BBC Two

Life is full of aphorisms ascribing properties to particular colours. The scarlet woman. Red light spells danger. Yet, according to the first in the new series of Horizon, colour is “one of nature’s great illusions”. Even so, wearing red reduces stress and increases confidence. This examination of how colour is seen and interpreted, and how it affects us, revealed that an awful lot of science bods are bothered about how and why we see what we see.

Why they’re bothered was immediately made clear. Colour can be linked to success. More Taekwondo players in red win than those in blue. Digitally reverse the colours in filmed competitions, show them to judges and the imposter reds are still awarded more points. A field experiment with footballers (who didn’t know what was going on) found the red shirts performing better, with higher levels of testosterone. Colour affects both behaviour and perceptions of behaviour. Job interviewees take note: red suits from now on.

Once the headline-grabbing stuff about red was dispensed with, Do You See What I See? unfolded as an examination of the processes of perception and interpretation. Red, green and blue cones in the eye see colour, but it’s up to the brain to decide how it should be filtered. It’s both subjective and unconscious. Painters might exaggerate individual colours, but the brain uses colour constancy to help recognise things – a banana is always a certain yellow however it’s lit.

An important trigger in reaching conclusions about what we see is the environment and how it’s used. The Vietnamese have 22 words for individual colours, the Namibian Himba tribe have five – they’ve no need for more and were shown being unable to describe a difference between green and blue. This was about more than the language of colour, part of a complex synergy between their day-to-day needs and environmental factors. Exactly how wasn’t spelt out, but they’re clearly fine with those five words.

A series of experiments on children were shown. They were conducted by the wonderfully named Surrey Baby Lab. Before we learn language, the experiment demonstrated, colour is processed by the right side of the brain. After acquiring language skills, colour is dealt with on the left side. Surely this was self-evident? Description of colour is with words, so it follows that the greater part of activity interpreting what’s seen would be facilitated by the parts of the brain that deal with language.

The colourfully shirted Dr Beau Lotto reached the more striking conclusion that colour can make time speed up and slow down. Colour affects other aspects of the rhythm of life. A restaurant bathed in blue light saw a marked increase of activity at 10pm. This was in keeping with our one-celled, ocean-dwelling ancestors that rose to the water’s surface seeking nourishment at times when less harmful ultra-violet light was around. We have our primate forebears to thank for being able to see red and green. They developed this facility (it was blue and yellow only beforehand) to help identify food. Although evolution found a visual way of determining what is and isn’t edible, no one asked why so much of the processed food that’s bad for us is yellow-orange or red: chips, fried chicken, pizza, the contents of frozen-food cabinets in supermarkets.

Some people can’t see colour – their eyes lack the cones – and train themselves that certain shades of grey represent green or blue. Others, not discussed in this gadflyish programme, through synaesthesia, can hear colour. Although these are extreme cases, the answer to "do you see what I see?" is obviously no. Unless you’re wearing red.

• Watch Horizon: Do You See What I See? on BBC iPlayer

Watch Mary Ellen Bute’s 1938 film, Synchromy No 4: Escape, an experiment in the relation between colours