You may have noticed this list makes no sense: color isn’t color til you see it. But let’s not get into all that. By ‘color’ we mean not only wavelengths but pigments and figments as well. When it comes to sight, though, we’ll be really, really pedantic!
A lot of these you’ll think you know. But not one have you actually seen—and you probably (or technically) never will.
10. Black
We’ve explained before why you’ll never see black: it doesn’t reflect any light. You wouldn’t even see it inside a black hole—and not just because you’d be dead.
We do have black paints and pigments, though. The blackest of these—those that trap the most light—are all in our list of weird paints. But here’s something new: there’s a “blackest black” fabric as well. Inspired by the gaboon viper’s ultrablack scales, viperblack absorbs 99.6% of all light that hits it. So, just like the blackest black paint, it seems to edit form from existence. Slimming indeed!
9. Stygian blue
The river that separates our world from Hades is so dark it’s darker than black, yet somehow discernibly blue (specifically lapis lazuli). You probably can’t imagine what it looks like… and you don’t have to, not exactly. If you stare directly at the spot in the yellow circle for 60 seconds, then at the black square below it, you’ll think you see stygian blue. You won’t see it… not really… but you’ll seem to.
This trick works with other colors too—for example staring at green for a stygian red or magenta and so on. And these stygian hues are only one type of the so-called impossible or chimerical colors. The other two are: self-lumimous (or ‘elysian’, perhaps?), colors that are brighter than white; and hyperbolic (olympian?), colors that are bolder than boldest, i.e. more than 100% saturation.
8. The Colour Out of Space
Without these tricks it’s hard to imagine a color that doesn’t exist. Even H.P. Lovecraft, with his boundless adjectival abyss, couldn’t quite capture The Colour Out of Space. Not that he wanted to, of course; its alienness was the whole point:
“It was just a colour out of space—a frightful messenger from unformed realms of infinity beyond all Nature as we know it; from realms whose mere existence stuns the brain and numbs us with the black extra-cosmic gulfs it throws open before our frenzied eyes.
[….]it was only by analogy that they called it colour at all
[….]that riot of luminous amorphousness, that alien and undimensioned rainbow of cryptic poison from the well—seething, feeling, lapping, reaching, scintillating, straining, and malignly bubbling in its cosmic and unrecognisable chromaticism.”
Though simple compared to Lovecraft’s other monsters, Colour is the hardest to recreate on screen. Director Richard Stanley’s 2020 version was a visual compromise (purple, mainly) involving experiments with heat and water and digital augmentation. The sound design was important for adding an alien feel. According to Stanley, the score includes ultrasound and infrasound, pushing “beyond the human auditory level … into forbidden frequencies.”
7. The color of infinite temperature
You won’t see this one for obvious reasons. Even the color shown here is just an approximation, and one that varies from screen to screen. Not only that but the CIE color spaces on which it’s based are themselves only the product of 17 volunteers’ observations back in the 1920s. Nevertheless, to see this color of infinite temperature as accurately as possible, set your monitor’s color temperature to 6,500k.
In case you’re wondering, it’s officially named perano. And it’s also (an approximation of) the color of a neutron star, as well as the early universe.
6. Hooloovoo
Another hue you won’t find on Earth (or even necessarily in space) is the fictional Hooloovoo: a super-intelligent shade of blue, at least compared to the others. In Hitchhiker’s Guide to the Galaxy, the Hooloovoo are an alien race from a faraway cluster of asteroids. They’re known for holding their breath until they turn purple to show dissatisfaction with the universe. And to interact with matter they refract into prisms.
They also had a cameo in Doctor Who. In The Rings of Akhaten (series seven, episode seven), the Doctor takes his new companion Clara to an alien market where, among other strange entities, they see a Hooloovoo striding about. Here, though, it just looks invisible.
5. Octarine
In Terry Pratchett’s Discworld novels, Octarine is the color of magic. As its name suggests, it’s the eighth color of the Discworld spectrum.
Although usually only visible to wizards and cats, non-wizards can glimpse it by closing their eyes. Try it now (assuming you’re not a wizard). Those colored flashes? They’re octarine, a kind of fluorescent greenish-yellow-purple.
It’s also the colour of magic in our world—at least according to chaos magicians. According to occultist Pete Carroll, however, it’s more of an electric pinkish purple than fluorescent green and yellow.
4. Reddish green
In addition to our three types of cone cell for different wavelengths of light (red, green, and blue), humans have two types of neuron for recreating color. Known as ‘opponent neurons’, they combine signals from the cones to get a true color value. One signals either red or green, while the other signals either blue or yellow. Neither signals both ways at once.
In other words, you can’t see a color that is both red and green; it’s forbidden by the way your vision works. Or is it…?
In 1983, visual scientists Crane and Piantanida claimed we could see reddish green. Their method involved staring at vibrant red and green stripes side-by-side until they bled into each other. To ensure a constant input of each of the colors, eye trackers held them steady relative to even the tiniest of eye movements.
But you too can get a rough idea of reddish green by crossing your eyes at the image above to bring the crosses together. It certainly isn’t brown. In the 1983 study, participants said the color was unlike any they’d seen—and one was an artist “with a large color vocabulary”. Although one follow-up study did conclude that red plus green equals brown, it didn’t make use of the eye trackers. This is a crucial component, as is the equal brightness of the side-by-side colors. When conditions are right, it’s said to be like seeing purple for the very first time while staring at red and blue.
To date, however, reddish green remains nameless, as does its forbidden color twin blueish yellow.
3. Infrared
Despite accounting for more than half the radiation reaching Earth from the Sun, infrared falls outside the visible range of humans and most other animals.
But this hasn’t always been obvious. With the invention of radar in World War Two, pilots were asked if they could see infrared from their cockpits.
More recently, scientists have reported seeing green flashes while working with infrared lasers. This has to do with the way photopigment molecules in the retina absorb incoming photons. Usually they absorb one each. However, the short rapid pulse of a laser beam can deliver two photons at once to a single photopigment molecule. And this effectively halves the wavelength.
So while one infrared photon is undetectable with a wavelength of 780-1000 nanometers, two infrared photons bring the same energy as a single 500 nanometer photon. This falls within the visible range. In fact, it’s green. In other words, you can’t see infrared but you can potentially see half of it.
2. Ultraviolet
At the other end of the spectrum is ultraviolet. A number of animals have cones for detecting this range (the mantis shrimp has six!) but usually it’s invisible to humans. This is partly because our lenses block ultraviolet from entering the eyes. Of course, we also lack UV cones; but the removal of one or both lenses—as in cataract surgery—allows us to catch a glimpse. And, when cataract surgery patients just so happen to be world-famous Impressionist painters, they can share this glimpse with the rest of us.
When Claude Monet at 82 had his left eye lens removed, not only could he see the old colors he’d lost, he could now see ultraviolet. This explains the ethereal hues of his later paintings—and their contrast to earlier works. In terms of light, they portray a blue-dominant mixture of red, green, and blue, or in other words white. It’s said he could even glimpse the UV patterns on petals evolved to guide bees toward pollen.
Interestingly, Allied military intelligence during World War Two recruited such people to watch for U-boats’ UV lamp signals.
1. Lunar complexion
When Domingo Gonsales touched down on the “Moone” in the late 1620s (arriving by a flock of wild swans), he was welcomed by its natives the Lunars. These tall Christian people were strange in many ways—not least for the color of their skin:
“I must tell you, it was a Colur never seen in our earthly World, and so neither to be described nor conceived by us; for as it is hard to make a Man born blind understand the Difference between Green and Blue, so neither can I decypher this Moon-colour, as having no Affinity with any I ever beheld; I can only say it was the most glorious and delightful that can be imagined, neither was any Thing more pleasant to me during my Stay there.”
The above is a quote from Bishop Godwin’s classic work of science fiction, The Man in the Moone, which according to some was the first of the genre. And there’s a reason he fixated on the Lunar complexion: his story deliberately alludes to the earlier, possibly true tale of the green children of Woolpit. This is the medieval English account of two green-skinned children, a boy and a girl, who appeared out of nowhere and spoke an unknown tongue. Later, when the girl learned English, she said they came from St. Martin’s Land, a distant place where the sun never shone and the sky was always in twilight.
By way of possible explanation, in Godwin’s novel the Lunars dispose of their own inferior children by dumping them on Earth (usually in America), after which they lose their green skin tone over time. Godwin’s Lunars are also devoted to St. Martin, on whose “island” the holiest live.
It’s unclear what gives them their complexion, though. It may be either their diet or the “ayre,” or possibly the earthshine. But you’ll probably not see it yourself.