From what I understand, humans can see red green and blue and everything in the middle. Some animals I’ve heard see more colors than us, so what’s to say that some things in nature are colors that we don’t see? Who’s to say that some apples are red? And instead a different color that we don’t have a name for because we can’t process it?
How can we tell if this “apple” is as a matter of fact “red”.
In: 75
Light comes in a continuous spectrum, it doesn’t inherently have discrete colors. Color is a thing of our perception. And our color perception comes in a combination of three types of cone-cells in our retina. [Short, medium and long](https://en.wikipedia.org/wiki/Cone_cell#/media/File:Cone-fundamentals-with-srgb-spectrum.svg) types. For example 500nm light excites quite a bit of a response from medium cone cells, less from long cone cells and even less of a response from short cone cells. We perceive it as sort of a [bluish-green](https://imgur.com/ae0IQ49).
If you mix yellow and blue paint, you get green paint. It’s because this is how your eyes interpret the mixed signal that is coming from the mixed paints.
A paint that’s out of your visible spectrum would appear as colorless water. Imagine a UV paint that you see as water but another species can see it and interprets as blue. If you mix it with yellow, for you the result would be s diluted yellow (like mixing water to the yellow paint). The other species would probably interpret it as a kind of green.
In such situation this is exactly what’s happening. There are some flowers with intricate patterns that we don’t see because they are in UV. Some bugs can see them. We instead see the visible components only, which gives us for example a plain white image of the same flower.
How we know it? We can make machines that see the UV for us and shifts the pattern into colors that we can see.
Another real world example could be mice. Mice can’t see red light. You can turn on a red lamp and it’s still darkness for them however we can see them in the red light. For them a red lamp looks the same whether it’s on or off. Similarly, for us a pot of hot water looks the same as a pot of cold water, although the hot water emits infrared light. A species that can see the infrared, could use a pot of hot water as lamp without us noticing, similarly for how we use red lamp on mice. That species could look at us in the dark just like we look at the mice.
Of course we can make machines that can see infrared for us and that machine would see the hot water as shiny.
Many flowers and some animals (including humans) actually have interesting patterns in ultraviolet.
Just because an object reflects light we can’t see doesn’t mean it doesn’t also reflect light we can see. A flower may be blue to us for example, but blue with ultraviolet spots to a bee.
As for things which reflect only colors we can’t see- glass is one. It reflects a fair amount of ultraviolet light, so we can see straight through it but something which can only see ultraviolet would not be able to see through glass very well. It would only be semi-transparent to them.
As for absolutes- the wavelengths of light are absolute, but our interpretation of them is almost entirely subjective. Red is red because we have decided it is red. Physically it is light with a particular wavelength which interacts with the cone cells in your eyes a particular way.
Through science, we can build sensors to detect and allow you to see light in other bands outside of our normal vision. This would allow you see and observe that light, probably in more ways than you ever could if you could see it naturally.
At least we can specifically say that “red” is a specific range of the visible light spectrum, and define the range of wavelengths.
[The same cannot be said for “brown”](https://youtu.be/wh4aWZRtTwU?si=lFER7hUEHB-mL086)
Color perception is weird. People think color are these set principles about reality, but they are not. Believe it or not … your WiFi signals and data signals your phone is using to communicate are actually colors, our eyes are just not tuned to perceive them.
You see, colors only exist in the sense of how they differ from each other. That’s it. So any “new” color wouldn’t look like anything but “a different color”. You could only ever describe it as what it’s “not”, not as what it “is”.
Some people can see those other wavelengths, flowers use other light wavelengths to attract pollinators too, so things like flowers would look different and anything else that uses those wavelengths too
We know some animals can see light on a wider spectrum than us, a little way into what we fall infrared and ultraviolet. Some things shine in those colors that we can’t see. Like some flowers look bland to us, but they’re bright and visible to an insect that can see that light.
Stephen King (I think) wrote a short story about some kind of predator (bear, maybe) that was born with a mutation that gave it a color that humans can’t see.
I’m color blind in a certain range.
One of the dashboards at work has a red/green/yellow stoplight for each process. The app developer chose a green and a yellow that I can’t discriminate. And there’s no other indication other than color.
The summary at the bottom says 3 red 4 yellow 12 green. All I can see is 16 yellow/green circles. Someone else can walk up and point to the four yellows quickly.
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