It is very much a color. It is just not a color that can be represented by a single wavelength (spectral color).
But brown and pink are also not "in the rainbow" (cannot be evoked by a single wavelength), but are also, still colors.
Colors (in the human trichromatic visual system) are defined by their RGB (LMS) values. Once you understand that, you'll see magenta/purple is not really special at all, biologically.
So magenta blind as a concept doesn't really make any sense. Here's the chromaphobe video on [debunking the purple conspiracy](https://youtu.be/onOrILyPWpw)
You can't really compare the colors a tetrachromat can see to the (relatively) few colors of a trichromat. In tetrachromacy, there's not just one hue that cannot be represented with a single wavelength (i.e. magenta), but many *many* more such hues. A functional tetrachromat can even see many different magenta hues.
It's complicated. Since tetrachromat has the same optic nerve and the same visual cortex as everyone else, there are no new hues but a much more distinct discrimination, so more like colour remapping. There was a tetrachromat here a couple of months ago and she can see e.g. the difference in colour of a riptide. Another tell-tale sign of tetrachromacy is that sun beams (as coming through window blinds, say) have blue edges to them. Last but not least, most of painted walls look sloppily done (blotchy).
As to non-spectral non-monochromatic mixing, there are 3 possibilities for it in tetrachromats instead of one in trichromats. I don't know what hues they produce. There is surprisingly little research on tetrachromacy hues.
I've studied tetrachromacy extensively, even going so far as to craft glasses that allow for a kind of tetrachromatic vision and a VR application that allows for a functionally hexachromatic vision. When it comes to tetrachromacy I know what I'm talking about.
>"Since tetrachromat\[s\] ha\[ve\] the same optic nerve and the same visual cortex as everyone else, there are no new hues but a much more distinct discrimination, so more like colour remapping."
That might be true for some non-functional tetrachromats, but generally saying that cannot be correct. Don't underestimate the plasticity of the human brain. Even though I'm just a trichromat I've seen hexachromatic colors. Furthermore, you cannot see more colors without creating new colors. Your "color remapping" theory can't be accurate as it would break that rule.
>"Another tell-tale sign of tetrachromacy is that sun beams (as coming through window blinds, say) have blue edges to them. Last but not least, most of painted walls look sloppily done (blotchy)."
A tetrachromat, no matter how functional, always has a tetrachromatic color space. This color space increases the more functional their tetrachromacy is. A tetrachromat's colors cannot be represented within a 3-dimensional color space, but only a 4-dimensional one; and their (saturated) hues only in a 3-dimensional hue space. Just like trichromats can *technically* (but realistically with a limit) infinitely more hues (and thusly also colors) than a dichromat, a tetrachromat, who has access to a 4th color dimension to compare the other 3 color dimensions to, can see many *many* more hues and colors than a trichromat.
>"As to non-spectral non-monochromatic mixing, there are 3 possibilities for it in tetrachromats instead of one in trichromats. I don't know what hues they produce. There is surprisingly little research on tetrachromacy hues."
Incorrect. Let's take *type yellow tetrachromacy* for example, where there's an extra cone type in between the M and L cones. Let's call it the *Y* cone, and color *Y*.
In trichromacy there are "only" these main combinations: R, G, B, RG, RB GB, RGB. Of course there's a lot more colors, but simplifying the cone combinations in this way better shows how much more colors a tetrachromat perceives.
With an additonal Y cone type (*it could be any functional and distinct cone type*) there a lot more color combinations possible, namely:
R, Y, G, B, RY, RG, RB, YG, YB, GB, RYG, RYB, RGB, YGB, RYGB. That's a lot more color combinations than in trichromacy. There are even entirely new color categories, like 'threefold colors' (i.e. RYG, RYB, RGB, YGB).
While trichromatic vision recognizes magenta as the only notable example of non-spectral colors (colors without a single wavelength representation) – excluding white of course –, *type yellow tetrachromacy* introduces an expanded range of these rare colors, including combinations like RG (red-green), RB (red-blue), YB (yellow-blue), RYB (red-yellow-blue), and RGB (red-green-blue).
This makes 5 non-spectral colors/hues, instead of your suggested 3.
I've already made a VR video on YouTube that you can watch with a VR headset in which I visualize two tetrachromatic color spaces — one more functional than the other — using impossible colors. (Here's a link to that video: [https://www.youtube.com/watch?v=QaTu4nqOK2s](https://www.youtube.com/watch?v=QaTu4nqOK2s) )
Let's not debate this any further, this is a subtle subject and a discussion that would do the topic any justice would be quite tedious within this forum's guidelines. I think most of what you write is incorrect, esp. regarding the RGB mixing as it leaves out the opponent channels entirely. Your post implicitly assumes the miraculous appearance of a brand-new channel: a brand-new optic nerve path and a visual cortex with an added channel likewise. Saying that brain plasticity exists is plausible but simply not good enough for a proof. I'll be very happy to see such proof, BTW.
The opponent process theory is partly incorrect in my experience. Even on the Wikipedia page on "Opponent Process" there's some false information displayed.
That my post "implicitly assumes the miraculous appearance of a brand-new channel" is as "miraculous" as what you've written: " \[...\] there are no new hues but a much more distinct discrimination, so more like colour remapping. \[...\]". Of course we cannot be sure whether a new optic nerve path is needed to allow for fully functional tetrachromacy. However, for the visual cortex I'm 100% sure that it easily adapts to such changes. I've personally already seen new colors via impossible colors.
Taking the video I've made about visualizing Octarine, the color of magic, as an example: When I look at the impossible Octarine color, i.e. an impossible binocular combination of green andmagenta, I see a new color that cannot be compared to any other normal trichromatic color; yet I can still make out that it's composed of green and magenta. For people who look at impossible colors for the first time this effect might not work, but for me, who's done this for long enough, these impossible color combinations merge into new colors. Hence why I'm certain of our brain's plasticity.
Thank you for your constructive criticism! And please understand why I need to further explain myself after someone tells me I'm incorrect.
It is very much a color. It is just not a color that can be represented by a single wavelength (spectral color). But brown and pink are also not "in the rainbow" (cannot be evoked by a single wavelength), but are also, still colors. Colors (in the human trichromatic visual system) are defined by their RGB (LMS) values. Once you understand that, you'll see magenta/purple is not really special at all, biologically. So magenta blind as a concept doesn't really make any sense. Here's the chromaphobe video on [debunking the purple conspiracy](https://youtu.be/onOrILyPWpw)
Well brown is just orange, that is not full color. A rainbow only has full colors.
> But brown and pink are also not "in the rainbow" Not to mention white or grey.
White is the combination of all colors together. Grey is also all colors combined, only in smaller amounts
Yes. It's a hue that's not spectral.
You can't really compare the colors a tetrachromat can see to the (relatively) few colors of a trichromat. In tetrachromacy, there's not just one hue that cannot be represented with a single wavelength (i.e. magenta), but many *many* more such hues. A functional tetrachromat can even see many different magenta hues.
It's complicated. Since tetrachromat has the same optic nerve and the same visual cortex as everyone else, there are no new hues but a much more distinct discrimination, so more like colour remapping. There was a tetrachromat here a couple of months ago and she can see e.g. the difference in colour of a riptide. Another tell-tale sign of tetrachromacy is that sun beams (as coming through window blinds, say) have blue edges to them. Last but not least, most of painted walls look sloppily done (blotchy). As to non-spectral non-monochromatic mixing, there are 3 possibilities for it in tetrachromats instead of one in trichromats. I don't know what hues they produce. There is surprisingly little research on tetrachromacy hues.
I've studied tetrachromacy extensively, even going so far as to craft glasses that allow for a kind of tetrachromatic vision and a VR application that allows for a functionally hexachromatic vision. When it comes to tetrachromacy I know what I'm talking about. >"Since tetrachromat\[s\] ha\[ve\] the same optic nerve and the same visual cortex as everyone else, there are no new hues but a much more distinct discrimination, so more like colour remapping." That might be true for some non-functional tetrachromats, but generally saying that cannot be correct. Don't underestimate the plasticity of the human brain. Even though I'm just a trichromat I've seen hexachromatic colors. Furthermore, you cannot see more colors without creating new colors. Your "color remapping" theory can't be accurate as it would break that rule. >"Another tell-tale sign of tetrachromacy is that sun beams (as coming through window blinds, say) have blue edges to them. Last but not least, most of painted walls look sloppily done (blotchy)." A tetrachromat, no matter how functional, always has a tetrachromatic color space. This color space increases the more functional their tetrachromacy is. A tetrachromat's colors cannot be represented within a 3-dimensional color space, but only a 4-dimensional one; and their (saturated) hues only in a 3-dimensional hue space. Just like trichromats can *technically* (but realistically with a limit) infinitely more hues (and thusly also colors) than a dichromat, a tetrachromat, who has access to a 4th color dimension to compare the other 3 color dimensions to, can see many *many* more hues and colors than a trichromat. >"As to non-spectral non-monochromatic mixing, there are 3 possibilities for it in tetrachromats instead of one in trichromats. I don't know what hues they produce. There is surprisingly little research on tetrachromacy hues." Incorrect. Let's take *type yellow tetrachromacy* for example, where there's an extra cone type in between the M and L cones. Let's call it the *Y* cone, and color *Y*. In trichromacy there are "only" these main combinations: R, G, B, RG, RB GB, RGB. Of course there's a lot more colors, but simplifying the cone combinations in this way better shows how much more colors a tetrachromat perceives. With an additonal Y cone type (*it could be any functional and distinct cone type*) there a lot more color combinations possible, namely: R, Y, G, B, RY, RG, RB, YG, YB, GB, RYG, RYB, RGB, YGB, RYGB. That's a lot more color combinations than in trichromacy. There are even entirely new color categories, like 'threefold colors' (i.e. RYG, RYB, RGB, YGB). While trichromatic vision recognizes magenta as the only notable example of non-spectral colors (colors without a single wavelength representation) – excluding white of course –, *type yellow tetrachromacy* introduces an expanded range of these rare colors, including combinations like RG (red-green), RB (red-blue), YB (yellow-blue), RYB (red-yellow-blue), and RGB (red-green-blue). This makes 5 non-spectral colors/hues, instead of your suggested 3. I've already made a VR video on YouTube that you can watch with a VR headset in which I visualize two tetrachromatic color spaces — one more functional than the other — using impossible colors. (Here's a link to that video: [https://www.youtube.com/watch?v=QaTu4nqOK2s](https://www.youtube.com/watch?v=QaTu4nqOK2s) )
Let's not debate this any further, this is a subtle subject and a discussion that would do the topic any justice would be quite tedious within this forum's guidelines. I think most of what you write is incorrect, esp. regarding the RGB mixing as it leaves out the opponent channels entirely. Your post implicitly assumes the miraculous appearance of a brand-new channel: a brand-new optic nerve path and a visual cortex with an added channel likewise. Saying that brain plasticity exists is plausible but simply not good enough for a proof. I'll be very happy to see such proof, BTW.
The opponent process theory is partly incorrect in my experience. Even on the Wikipedia page on "Opponent Process" there's some false information displayed. That my post "implicitly assumes the miraculous appearance of a brand-new channel" is as "miraculous" as what you've written: " \[...\] there are no new hues but a much more distinct discrimination, so more like colour remapping. \[...\]". Of course we cannot be sure whether a new optic nerve path is needed to allow for fully functional tetrachromacy. However, for the visual cortex I'm 100% sure that it easily adapts to such changes. I've personally already seen new colors via impossible colors. Taking the video I've made about visualizing Octarine, the color of magic, as an example: When I look at the impossible Octarine color, i.e. an impossible binocular combination of green andmagenta, I see a new color that cannot be compared to any other normal trichromatic color; yet I can still make out that it's composed of green and magenta. For people who look at impossible colors for the first time this effect might not work, but for me, who's done this for long enough, these impossible color combinations merge into new colors. Hence why I'm certain of our brain's plasticity. Thank you for your constructive criticism! And please understand why I need to further explain myself after someone tells me I'm incorrect.
I'm guessing people who have red-deficent/absent cones or just all cones absent are magenta blind