I have devised a semi-aquatic sapient species known as the Hexapi who until now I thought were trichromats. However, after doing my research on the evolution of the eye, I found out that colour vision may be a disadvantage underwater. As I didn't want to give them polarised light vision, I decided to give them tetrachromacy. I know the case of Concetta Anticco, who sees the world psychedelically, just like birds. I've also known that tetrachromacy enhances colour sensitivity in shadows and dim lighting. Here's the problem, though. The Hexapi carry chromatophores on their skin.

My question - How would they reliably communicate with chromatophores? How would they look to humans?

Notes - The hexapi rarely dive below 50m (~150ft) and live in rich, shallow waters. They also sport colourful striped displays on each of their 2 side 'fins', which are of course only visible to them.

  • $\begingroup$ Do you like Star Trek over the newer Battlestar Galactica? In Trek they techno-babbled everything, or nearly so. In BSG on the other hand: what do you need, got it, cut to action. I have several species in my own universe that have had space travel for millennia. Why they do something? That is the past or 'that is how it is' and they move on. Don't dwell on the minutia, move the plot forward. Trying to communicate with other species can be explored per instance, this species, their methods/body/limitations. Just imagine them, describe that, work out details later, if at all. $\endgroup$
    – dcy665
    Aug 4, 2017 at 23:51

1 Answer 1


Color is a sensation which happens in the mind. It it not a physical quantity, it does not exist in nature. There is no way to compare the color sensations of humans and non-human animals, especially imaginary animals. Consider bees; they are trichomats like us, but their primaries are green, blue and ultraviolet: red appear black to them, ultraviolet appears black to us...

Tetra-, penta- or hexachromacy has no relationship whatsoever with light sensitivity. For example, in dim light humans switch color ("photopic") vision off completely and activate a separate monochromatic ("scotopic") low-resolution high-sensitivity system.

Real-life squid (intelligent animals which live in water) have an entirely different system for color vision. Instead of using multiple types of photosensitive cells, like us, they have only one kind of photoreceptors and use their lenses to bring various wavelengths in focus successively... which, one can speculate, makes their "color" vision more like our auditive sensations, that is, perceiving each wavelength separately, like a musical chord.

  • $\begingroup$ Forget animals, we can't describe color between individual humans in a reliable way to ensure that what I see is red is the same color that you see as red... Now, if I say it's red like an apple, and you say yes, that is correct, it doesn't establish that your perception of what is red is the same as mine. You're mind may make red what my mind makes purple... and we'd never know, because an apple is still a red fruit and that's the best we can get at describing what red is supposed to look like. $\endgroup$
    – hszmv
    Aug 4, 2017 at 18:25
  • $\begingroup$ @hszmv: For humans, who can speak and follow instructions, there is an empirically well-defined "standard observer" defined by the International Commission on Illumination (CIE, from its original French name, Commission internationale de l'éclairage), for which a standard "general human" colorspace, CIE L*a*b* has been empirically measured; in practice, empirical experimentation shows that the vast majority of women, and about 3 men out of 4, perceive color quite close to what is expected of a standard observer. $\endgroup$
    – AlexP
    Aug 4, 2017 at 18:33
  • $\begingroup$ I am refering to en.wikipedia.org/wiki/Qualia "Qualia" which is different. I ceed that the scienfic measure of a color corresponds to a particular wave length, computer information storage range, and description general items of that color. I also cede the symptoms of colorblindness as a defect in the ability to parse one particual color. Where my arguement lies is in the experience of that color. You and I can agree that green is a range of electromagnetism that our brain parses into a visiual component... but we cannot know if we parse it the same way (cont). $\endgroup$
    – hszmv
    Aug 4, 2017 at 18:58
  • $\begingroup$ We can agree on the consistency of the parse between any two individuals, but we cannot know if that parse consistently looks the same between two indivuals. $\endgroup$
    – hszmv
    Aug 4, 2017 at 19:01
  • $\begingroup$ @hszmv: Color is not wavelength, but rather it is related to the spectral composition of light, at least for objects which occupy a large enough part of the visual field; for example, computer screens do not emit any "yellow" wavelength, but have no problem showing the color yellow. For another example, there is no wavelength producing purple: purple is what is called a non-spectral color. And as for the comparison of internal sensations, I agree that it is impossible. $\endgroup$
    – AlexP
    Aug 4, 2017 at 19:06

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .