New colors without shooting lasers into your eyes

For whatever reason, evolution decided those wavelengths should be overlapping. For example, M cones are most sensitive to 535 nm light, while L cones are most sensitive to 560 nm light. But M cones are still stimulated quite a lot by 560 nm light—around 80% of maximum.

The reason is simple: genes coding the long wave opsins (light-sensitive proteins) in these cones have diverged from copies of the same original gene. The evolution of this is very interesting.

Mammals in general have only two types of cones: presumably they lost full color vision in the age of dinosaurs since they were primarily small nocturnal animals or lived in habitats with very limited light (subterranean, piles of leaves, etc.) Primates are the notable exception, and have evolved the third type of cone, enabling trichromatic color vision, as a result of their fruitarian specialization and co-evolution with the tropical fruit trees (same as birds, actually).

So, what's interesting is that New World and Old World primates evolved this cone independently. In Old World primates the third cone resulted from a gene duplication event on the X chromosome, giving rise to two distinct (but pretty similar) opsin genes, with sensitivity peaks at very close wavelengths. As a note, because these genes sit on the X chromosome, colorblindness (defects in one or both of these genes) is much more likely to happen in males.

New World primates have a single polymorphic opsin gene on the X chromosome, with different alleles coding for different sensitivities. So, only some (heterozygous) females in these species typically have full trichromatic vision, while males and the unlucky homozygous females remain dichromatic.

Decent wikipedia article on the subject: https://en.wikipedia.org/wiki/Evolution_of_color_vision_in_p...

Types of opsins in vertebrates: https://en.wikipedia.org/wiki/Vertebrate_visual_opsin

To me it looked like the circle outline had a shimmering aura, it felt very magical. This was a incredibly delightful experience so I just want to say thanks for posting it.

When the circle was around the halfway point of shrinking the color looked the most vivid for me, so be sure to wait the whole duration.

A bit unrelated but I found this interesting: water is transparent only within a very narrow band of the electromagnetic spectrum, so living organisms evolved sensitivity to that band, and that's what we now call "visible light".

http://hyperphysics.phy-astr.gsu.edu/hbase/Chemical/imgche/w...

I did a custom combination of yellow outer field, blue inner circle, and got a vibrant purple halo, which is not what I expected. I assumed it would be "yellow++", based on what I know about the human eye's colour sensitivity.

I didn't expect a strong effect, because the overlap between blue and red/green is so much less than the overlap between red and green, but bright purple is close to the opposite of what I expected. I'm genuinely puzzled.

"If you’re colorblind, I don’t think these will work, though I’m not sure."

Should work for anomalous trichromats (by far the majority of people with color deficiencies) but probably with less intensity.

"Folks with deuteranomaly have M cones, but they’re shifted to respond more like L cones."

I don't think this is true. What would the difference between deutan and protan then be?

"Why do you hallucinate that crazy color? I think the red circle saturates the hell out of your red-sensitive L cones. Ordinarily, the green frequencies in the background would stimulate both your green-sensitive M cones and your red-sensitive L cones, due to their overlapping spectra. But the red circle has desensitized your red cones, so you get to experience your M cones firing without your L cones firing as much, and voilà—insane color."

I think only people with missing L cone (Protanopia) or M cone (Deiteranopia) would not experience the phenomenon at all.

Maybe this could be used as a new type of color deficiency test?

Incidentally the linked Skytopia page is that of Daniel White, who originally described the Mandelbulb: https://www.skytopia.com/project/fractal/mandelbrot.html / https://www.skytopia.com/project/fractal/mandelbulb.html

> If you refused to look at the animation, it’s just a bluish-green background with a red circle on top that slowly shrinks down to nothing. That’s all. But as it shrinks, you should hallucinate a very intense blue-green color around the rim.

I do not believe I have any kind or amount of colorblindness, so imagine my surprise when extremely confused I pulled the image into MS Paint, used the Color Picker tool, and found that indeed, the background has quite a bit of blue in it.

Anyhow, I cannot reproduce the illusion cited. For me the circle just blurs out and I start seeing orange.

I am curious how these work for people with common kinds of colorblindness. The author mentions at the end that they likely don't work for that case, but they don't seem to have spent much time thinking about it.

Would it be possible to generate ones that _would_ work for specific kinds of colorblindness? Or is the entire concept doomed due to the specific way(s) that colorblind eyes are messed up?

Is this just my device, or is there no way to use this roll-your-own SVG generator to actually roll your own? I can only pick from a tiny subset of preset colors, most of which seem super random and desaturated and not what I want. There's no FFFF00 yellow, for instance. Is there some way to enter an arbitrary RGB color that I am not seeing? If not, why on Earth write such an interesting article, advertise this custom SVG generator and then build the interface that way? :/

I just want a display with a primary at 460nm. That's all I ask.

It is incredible to see a concept going from 'optical table of sensitive equipment fraught with numerous safety concerns' to 'here is a 1 kB svg animation, stare at it for 1 minute' in 3 months.

Enjoy your forbidden color, you earned it!

This is really cool. Tangentially, it's an example of an important life lesson, "work smarter not harder". To see the impossible color, you could build a super-expensive, super-complicated laser to directly stimulate the exact cells; or you could desensitize the other ones with an optical illusion that works on a personal device (effectively zero cost and minimal complexity since it uses existing technology).

Not to say the laser is a waste, despite the above I'd argue it's very useful. It lets us test how effectively the above actually works, and has other applications.