“A friend recently learned she was colour blind. She was quite surprised. In fact, the diagnosis came completely out of the black,” writes “Whimsy” columnist CLIVE WILLIAMS.
WHAT colour is the White House? It’s a trick question because technically white is not a colour.
When I was at school we learned an acronym for the colour spectrum – ROYGBIV (for red, orange, yellow, green, blue, indigo, violet) – and were told that white and black are not colours. But it’s not quite that simple.
The full range of colours – based on wavelength, frequency, and energy of light – should include infrared (before red), cyan (between green and blue) and ultraviolet (after violet).
Some consider white to be a colour, because white light comprises all hues on the visible light spectrum but, technically, black and white are not colours. Black is the absence of light. Unlike white and other hues, pure black can exist in nature without any light at all.
Human perception of colour begins with specialised retinal cells known as cone cells. They contain different forms of opsin – a pigment protein – that have different spectral sensitivities. Human eyes contain three cone types, resulting in trichromatic (three channel) colour vision. Our cones turn light and colour information into three separate signals: red, green, and blue.
The colours we see also depend on light absorption, reflection, and emission characteristics of what we are looking at. Our colour vision is poor in low light and peripherally.
In the animal world, some animals see very little colour, while creatures such as bees and butterflies can see more colours than humans.
Dogs possess only two types of cones that signal primary colours blue and yellow – this limited colour perception is called dichromatic (two channel) vision. Some scientists believe that cats only see blue and grey, while others think they also see yellow, like dogs.
What about birds and fish? Birds have additional cones in their retina that are sensitive to the ultraviolet range, so they can see colours that are invisible to humans.
The majority of fish have eyes that can detect the colours typical of their environment. For example, inshore fish have colour vision, whereas offshore pelagic fish have limited colour vision and can detect only a few if any colours. Sharks are colour blind and are thought to be confused and deterred by black and white stripes. A cuttlefish is colour blind but can change its colour for concealment. Whales and seals are also colour blind.
Why do bulls in bullfights hate red? Actually, they don’t. Bulls and other cattle are dichromatic and cannot see red. Bulls are irritated in a bullfight by the movement of the red muleta wielded by the bullfighter.
Why do some humans suffer from colour blindness? It’s commonly caused by a genetic fault – some colour-sensitive cones are either missing or do not work properly. (A friend recently learned she was colour blind. She was quite surprised. In fact, the diagnosis came completely out of the black).
Colour-blind people see normally in other ways and can still drive vehicles. At traffic signals they see them changing and know that red is at the top and green is at the bottom.
Blacker than black “Vantablack” (Vertically Aligned Nano Tube Array Black) is a unique, carbon nanotube-based pigment produced by British company NanoSystem. Vantablack was developed in 2014 for specialised military and space applications. It absorbs 99.965 per cent of light.
Against a deep black background objects coated in Vantablack seem to disappear. This is because the human eye perceives shapes coated in Vantablack as two-dimensional.
Vantablack is used for stealth aircraft and weaponry and sensitive telescopes that can detect the faintest of faraway stars. In 2019 engineers at MIT revealed a new, even darker black coating that is capable of absorbing 99.995 per cent of visible light.
To close with a colourful anecdote: A handsome American walks into an Australian pub with a big, beautiful, red, blue and green parrot on his shoulder.
The bartender says: “Wow! He’s awesome, where’d you get him?”
“California” the parrot replies.
* To refer back to the heading, the entire White House exterior is painted with Duron’s “Whisper White” exterior paint.
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