You see colour using three different kinds of cones in our eyes, and these cones can be either red, blue, or green. So where does yellow come in? Green consists of yellow and blue – but how would you only see yellow and not the blue that would make it green?
In: Biology
There’s literally a Veritasium video (https://www.youtube.com/watch?v=nfAqTSjMBJk) on this that just came out
Magenta doesn’t exist. Yellow is real but we can’t actually see it. Goldfish can. Yellow we guess, magenta we just make up
What you perceive — the image you see in your head — is just an invention of your mind as it processes signals from your optic nerves. In some sense, there is no “yellow” outside of a perceiving mind: there are merely objects reflecting waves of light. The image you “see” is based on physical reality, but it’s your own interpretation of it. For all we know, what I “see” in my head as “yellow” could be completely different from what you “see”. We can agree on what objects are “yellow” (assuming neither of us is colorblind), but not how “yellow” “looks” to us.
Here’s something that will really blow your mind: there’s an invention for blind people that consists of a pair of sunglasses equipped with a camera and a patch that sits on their tongue. The camera sends signals to the patch, which in turn zaps the user’s tongue (apparently it feels like pop rocks) based on the light picked up by the camera.
Given enough time and practice, blind people who use this device will eventually start “seeing” what the camera is picking up, even though their eyes aren’t involved at all. The brain doesn’t care where the signals are coming from, after all: all that matters is that visual data is being fed into the brain, which can then be interpreted as visuals, which can then be perceived. Given a sophisticated enough device (camera resolution + method of sending signals to the brain), there’s no reason someone couldn’t see perfectly normally, without a single cone being involved.
[https://www.scientificamerican.com/article/device-lets-blind-see-with-tongues/](https://www.scientificamerican.com/article/device-lets-blind-see-with-tongues/)
Our cones can perceive either red, green or blue but they are not perfect, so they react more to a specific wavelength corresponding to those three colours but they also react to other wavelengths that are close, a certain wavelength activates both green and blue and your brain interprets it as yellow
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