3. Secret Colors, Impossible Colors

 

 

This is a post about colors I can’t show you, because they don’t quite exist. You might ask, what does it mean for a color to be secret? How can a color not quite exist? The answer, approximately, is that the more you think about color, the less sense it makes. Maybe you want to flee, and keep your nice simple safe elementary school understanding of colors as something inherent to the world. Maybe you want to keep on thinking of color as being some mere function of surface reflectivity of visible light, as being something straightforwardly generated by adding light together - red and green and blue light combining to white - or as being something dual to that, equally simply generated by subtracting away light through absorption - cyan and magenta and yellow pigment combining to… not black, exactly, but close enough.

Maybe you’d even be alright thinking of color as something underspecified to do with retinal pigments, or mentally toying with the unknowable nature of individual color qualia. Perhaps you’ve even got as far as understanding the changing nature of color - the way a color gets displayed differently on different screens and monitors, or how inks and paints and fabrics look different on the wall of a specific bedroom compared to in an art gallery; the ways in which individual physical instances of “the same” color aren’t really the same color at all - and if you’ve got this far, it’s probably already too late for you. (Maybe it’s not too late. Maybe you could close this tab and burn your phone or computer and flee into the endless ignorant night. Maybe your dreams won’t be haunted by impossible colors. That’d be nice.)

Think about the nature of color too hard, and you lose that nice simple safe understanding of what color is. Think about the nature of color too hard, and you go mad. Let’s go mad.

Let’s begin by delving too deeply into a mystery from your childhood: you’ve been to Disneyland, right? Right. (Or if you haven’t, most other amusement parks will do.) Maybe you weren’t looking too closely or your memory’s a little fuzzy, but why were so many of the buildings red brick? Why were the walkways all in that shade of salmon-y pink? And just what was it that made the grass look so vibrantly green, even in your memories? It wasn’t just you; not just the innocence of a young child’s eyes, nor the sugar rush of the lemonade. This central dogma about color: light enters your eye, and it strikes and excites cone cells in long and medium and short wavelength flavors; then those excitations battle - red against green, blue against yellow - to produce the experience of hue. Together with the absolute level of light as given by your rod cells, you perceive color. Simple as, right? No way of perceiving colors apart from something to do with surface reflectivity somehow? Not so fast. Consider that cone cells - and rod cells too, for that matter - are basically differently specialized neurons… which means that after they propagate their action potential, there’s a brief refractory period before they can fire again. This, for example, is why you can be briefly blinded after looking at a very bright light. What this means for us in terms of seeing secret colors - more commonly called chimerical or out-of-gamut colors - is that we can trick our own eyes to glimpse the impossible.

Here’s how: pick a hue, any hue, and calculate its opposite - magenta for green, cobalt blue for bright orange, chartreuse for violet, red for cyan, that sort of thing. Stare deeply and unblinkingly into that backwards hue for thirty to sixty seconds, long enough for your cone cells to bleach a little. (Don’t worry. They’ll recover. Eventually. Probably. All knowledge has its price.) Then, depending on the class of chimerical color you wish to see, turn your gaze to your choice of white, your originally chosen hue, or black. If what you seek is a self-luminous color - a color as luminous as white and yet still possessing a hue - then look at a white background. If you prefer a stygian color - a color as dark as black and yet still clearly of some hue - then look at a black background. And if you, like me, seek a hyperbolic color - a color of some chosen hue with a saturation above anything pigment or light can achieve - then look at a background of your original color. Self-luminous, stygian, hyperbolic: the three main categories of chimerical color. All of them are achievable with a little patience and a phone screen; these days, you could probably hack together something straightforward with a VR headset. But there are others yet: opponent-process colors like redgreen and yellowblue which all but require a VR headset for careful luminosity calibration, and the newly experienced olo, and the actinic blue-white of ultraviolet light that only those lacking natural corneas can see. It would be foolishness to expect no more, to expect the messiness of human phenomenology to stop at these few enumerated possibilities when it already refused to constrain itself to the physical. Perhaps it was foolish to expect human color vision to limit itself to the physical, having already shunned mere spectral colors for magenta.

I lied a little at the beginning. I can totally show whole crowds some of these colors stably, even though they don’t quite exist. (By now, you understand why it’s not quite meaningful to speak of colors as clearly existing or not existing.) It’s just that I can’t show them to you except in person. There are deeper secrets yet in how to display these colors on physical objects for more than glimpsed seconds at a time; by evening dim one can see hyperbolic cobalt blue or hyperbolic chlorophyll green for whole minutes at a time without much special preparation at all, and maybe I will write about the trick of it another time.


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