A post by Neil Sinhababu.

I recently tried on color vision correction glasses that would help me see green for the first time. In addition to being excited about seeing green, I was curious about whether I’d see a color I wasn’t able to imagine before. I think I did! Amy Kind suggested that I tell you about my color imagination experiment, so here I go.

For me, green has always sort of flattened into brown rather than being a fully independent color. This sometimes caused me to do funny things. In kindergarten I drew myself with the green crayon rather than the brown crayon. In 9th grade a classmate told me that the boy I had drawn on a poster had green hair (I thought it was brown). I discovered my problem in high school when our family optometrist did tests to confirm that I had bad color vision. In college, my friends had me play a color-matching puzzle video game against my similarly impaired roommate. When we shouted with surprise at our repeated mistakes, our friends laughed with (depraved?) amusement.

I’ll summarize this extensive account of how color vision works, how it fails in cases of impaired color vision, and how Enchroma color vision glasses fix it. You see colors when the red, green, and blue cones in your eye get stimulated by the appropriate wavelengths of light. But due to a genetic mutation that affects a protein that goes into my red and green cones, they’re both activated by some wavelengths of light that would activate only green in normal people. So green light that includes these wavelengths makes me experience a muddled brownish-green. Enchroma glasses work by blocking the muddling wavelengths, but letting through some green and red wavelengths that don’t cause erroneous activation of the wrong cone type. This allows for purer and more vivid red and green experiences.

The effect of the glasses isn’t quite as dramatic as I had hoped. Like sunglasses in general, they work best in very bright sunlight, since they block off enough light to merely make everything darker in dimmer conditions. I tried them on first a bit too soon before sunset, and they didn’t have any real effects except making things darker as sunglasses would. My sister, who took the picture above, also took video of my first experience with the glasses but it’s not especially interesting, since things weren’t very different.

I went through Enchroma’s online color vision test before buying the glasses and then again with the glasses on. I got the same result with and without the glasses: moderate deuteranomaly. This is “a type of red-green color blindness in which the green cones do not detect enough green and are too sensitive to yellows, oranges, and reds.” Like the evening sun, my monitor isn’t bright enough.

But in bright sunlight, the glasses seem to have a real effect in deepening greeness and redness. They turn down the yellowish brightness of the sunlight, while giving green more of its depth as an independent color. I didn’t expect this effect with redness – it may be more pronounced than the effect on greenness. I think the image-editing way to put this is that it raises the saturation of these colors.

One of the early exciting moments came when I looked at a green traffic light with the glasses on. I knew that the bottom light looked green to other people because they called it the green light, but to me it just looked like a dirty off-white. (Ever since Dr. Lilyquist gave me the color vision test in high school, I accepted that my color vision was impaired and everyone else was getting it right.) But suddenly it had a rich explosion of vivid color! And that was green. I guess traffic lights have to shine brightly even in bright sun, so they’re very good light sources for this purpose.

I’m not certain about this, but I don’t think I ever previously saw or imagined the deep but vivid green that I’ve now experienced when wearing the glasses and looking up at the sunlight glowing through summer foliage. I’ve had a few experiences like this since getting the glasses – in a North Carolina park I used to visit in my childhood and during some unusually sunny Oxford days this June. (Yeah, I’m traveling a lot! This is the victory lap of a big crazy post-tenure sabbatical lecture tour where I already gave 114 talks in 365 days.)

Before I put on the glasses for the first time, I kept trying to imagine the most intense green that I could. I found that I was either adding yellow for general brightness, or adding white for a somewhat shiny glare that was often present when people described things as bright green, or adding blue to give the color a different kind of depth. But none of these really seemed to make things more green. (As a check on expectation-based cognitive penetration, I answered some questions before putting on the glasses, and this was one of them.) There were more obviously wrong options – adding red would push me further in the brown direction, and darkening green with more blackness was obviously something different. None of these moves got me to the color I’ve seen in sunlight shining down through layers of leaves.

Maybe there’s something I could’ve done to imagine deep green that I didn’t think of doing at the time. Maybe I didn’t know which color-direction to push my imagination in. Maybe there’s some deep metaphysical impossibility in imagining a color you haven’t seen. I don’t think my inability to imagine deep green is anything so deeply metaphysical – it seems more like a psychological phenomenon. I don’t know enough about the mechanics of imagination to know which of many psychological stories about it is the right one to tell. But I think that I’ve now seen a green that I couldn’t previously imagine.

Now, I can’t be totally certain that I’ve seen a new color. After all, the effects of the glasses on my green perception aren’t that drastic even under the best conditions. I assign about a 10-15% probability to the supposedly new greens I see being colors I’ve seen before, with some kind of cognitive penetration confusing me about my own visual experience. Everything certainly looks different, but did I really have a new experience, and not an experience I’d had visually or in imagination before, transferred to a new location? And maybe I’m just mistaking the novelty of this experience there for the novelty of a totally new experience? Maybe, I guess. Hard to know how strong cognitive penetration is, or how it works.

But my best guess is that these glasses really did show me a pretty new color. It’s a deep, vivid, rich green that’s further in the green direction than anything I’d experienced before. After a month of occasionally wearing the glasses, it seems to me that when I imagine sunlight through forest leaves, I imagine a pretty new color too.