Colour Me…??

I don’t decorate with red and green for Christmas.

Ironic, because red was my favourite colour when I was a child, and it is an attractive combination. I don’t mind it in small doses, but in large amounts it does tend to smack you in the eye.

Is that holiday heresy? Probably in some people’s minds

But I find it fascinating that red-green deficiency is the most common form of ‘colour blindness’.

We see colour as light waves enter our eyes and strike the retina in the back of them, activating special cells called rods and cones. These cells send electrical signals to the brain through the optic nerve, where the thalamus processes the signals and relays them onward to the visual cortex, where a variety of cells make sense of the information. Some of these cells react to colour, some to motion, some to shape and other types of information. Everything then comes together to provide us with identification about an item, such as its colour.

The cones detect colours in the visible spectrum of light – all of the wavelengths that creatures are able to see. When I was studying the behaviour of lizards for my university thesis, I was able to watch them with red light, which their eyes were unable to pick up. (My fellow students jokingly referred to my experimental setup as the lizard red-light district.)

Humans are usually born with three types of cones:

Red-sensing cones, which register long wavelengthsGreen-sensing cones, for middle wavelengthsBlue-sensing cones, for short wavelengths

Full-colour vision is called trichromacy – all three types of cones are present and working properly. In people with colour blindness, some of the cones in their eyes are either missing or not working properly. Colour blindness is an inherited condition, but it can also happen from environmental causes (exposure to some chemicals, certain medications) and from some medical conditions.

There’s currently no cure for colour blindness. Special glasses can enhance the contrast between colours to make differences between them more clear, but they can’t allow wearers to see new colours or fix the problems with the cones.

Maybe some day there will be a cure; new things are being invented all the time.

The colours that we can see are myriad and fascinating, at least for a lot of us. I can’t imagine walking around a garden and not being able to take in all the wonderful colours in it.

Flora (and a Monarch butterfly) from a variety of gardens — all photos by E. Jurus, all rights reserved

But what about colours in other wavelengths – the ones we humans can’t see?

Bees, for example, can see blue and yellow, but also UV light. When they look at flowers, they see patterns we can’t discern, like rings and stripes, which draw them in like guided landing marks toward the pollen they seek.

Rats can also see ultraviolet light, as well as green and blue, but not red. Some snakes are able to see infrared light, which means that they can sense heat signatures. Birds see as many as five to seven colours!

And what if there were colours we couldn’t make out no matter what, but that aliens from other planets could?

That’s an idea I’ve explored considerably in my Chaos Roads trilogy. Romy, my heroine, finds out in the second book that she can see many more colours than the people around her can. Not only that, but as she deciphers the Map of the Universe (an impossibly rare document on Earth that lays out the information needed to travel to other planets), each planet in the galaxy has its own unique colour signature.

Is that totally far-fetched? Well, you be the judge.

Wrinkled aluminum foil with a portion—equally wrinkled—coated in Vantablack — By Surrey NanoSystems – Surrey NanoSystems, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=34139562

Several years ago, researchers discovered how to make a black colour so dark that it absorbs 99.965% of visible light. It was given the name Vantablack, afterthe vertically aligned nanotube arrays (VANTAs)that are used to produce it (I’ll explain more in a second). Light becomes trapped and deflected among the nanotubes, eventually absorbed and let off as heat. If you look straight at something painted in that colour, you can’t make out any texture – in the above photo of a piece of crumpled foil, you can’t see any of the ridges. What would someone do with this colour, apart from cool-looking artifacts? It can be used to keep stray light from what’s called ‘skyglow’ (light from the moon, or light pollution) out of telescopes to make it easier to see fainter objects, and could also provide intense camouflage for the military.

In September 2019, at the International Motor Show Germany, BMW unveiled an X6 concept car painted with Vantablack. Take a look at this photo of it, and notice the numerous spotlights surrounding the car – I suspect that without them, we’d hardly be able to make it out. Now imagine a similarly painted vehicle, but without shiny/glossy parts like the chrome and glass – i.e., in stealth mode. At night, it would be impossible to see it until it ran you over.

BMW X6 Vantablack at the International Motor Show Germany 2019 — By Alexander Migl – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=82052265

There are colours that have been lost to history. We can see them in ancient artworks, but don’t know how they were made and can’t reproduce them. One such colour that’s come back to life is called Maya Blue. It was used in Mexican wells called cenotes, which were graveyards of human remains, where the blue colour served a ritual purpose. It’s also been found on pottery, sculptures, wall murals and paintings.

The colour was manufactured by the Maya and Aztecs, and fortunately was extremely resistant to weathering, or we’d never have known it existed. But eventually the technique to make it was lost – until 1993, when a Mexican historian and chemist, Constantino Reyes-Valerio, figured out how to do it. Maya blue was produced by combining indigo, a deep blue colour from the añil shrub which is native to the tropical and subtropical Americas, with different clays.

Baltasar de Echave Ibia painting with Maya blue — credit: BBC shareable articlewww.bbc.com/culture/article/20180816-the-rare-blue-the-mayans-inventedfrom Museo Nacional de Arte de Mexico

Other colours have been so toxic to make and use that they remain only in artifacts – pieces of artwork, or pottery. For example, a paint called Lead White was made as far back at ancient Greek and Roman times by soaking lead metal in vinegar and then scraping off the white powder that formed. It had an interesting colour, slightly creamy with perhaps a very faint tinge of grey, was very thick, and dried quickly. Artists loved it, and it was also used in cosmetics to whiten the skin. What no one realized was that lead can be breathed in or absorbed through the skin, and can cause long-term damage to the brain and kidneys. Many artists developed something called “Painter’s Colic” – lead poisoning. It wasn’t until the 1970s that the use of Lead White was officially banned.

In the early 1800s, German colour-maker Carl Wilhelm Scheele released a shade of green so vibrant that it became all the rage in Victorian high society. It was described as the colour of ‘life’ – the greenness of gardens. For city dwellers, who lived amid the gray, ugly smog created by the Industrial Revolution, the fresh green of Scheele’s green was irresistible. And with new gas lamp technology making rooms brighter, the colour was shown off to great effect, not only in beautiful ladies’ gowns, but also in wallpaper, carpet, and even faux plants – until people began to become violently ill. Families started vomiting in their green-painted homes, women wearing Scheele’s Green garments developed blisters. One maker of fake flowers, Matilda Scheurer, had an awful death after even the whites of her eyes turned green.

Assortment of gowns in Scheeles Green – collage from Reddit, source unattributed

Judging by this group of photos of gowns in Scheele’s Green, it was a gorgeous colour – but unfortunately it was made with arsenious oxide, i.e. arsenic. As the dangers became known, other less toxic green shades were developed. There’s now an RGB code that’s supposed to represent Scheele’s Green, but as you can see from this colour chip, it doesn’t really come close. If Carl Scheele hadn’t stumbled across the formulation, we’d have no idea that his dazzling green shade ever existed.

How many other colours once existed that we’ll never see, or might have existed if some enterprising person had discovered them? What other wavelengths exist out in space, unknown to us and never visible because our eyes simply can’t see them? Food for thought