TLDR: A display for people or other creatures with true tetrachromatic vision (not just an additional receptor, but the ability to perceive it as a distinct pri

TLDR: A display for people or other creatures with true tetrachromatic vision (not just an additional receptor, but the ability to perceive it as a distinct primary colour) would need to be able to output that fourth primary colour, but there doesn't seem to be enough data to determine conclusively at this time if women with a fourth type of cone perceive a fourth primary colour. The one study I've been able to read the full text for that involved determining spectral sensitivity of a woman with distinctly tetrachromatic vision[1] indicates that she had some cones with a peak in-between what most people would see as red and green,[2] and could consistently and accurately discriminate between colours that would appear identical to most people.[3] Unfortunately (and surprisingly, IMO), it doesn't discuss her subjective perception, i.e. does she perceive a true fourth primary colour? It seems like a very, very rare gift, so IMO it's hard to even determine if the women who have it respond in similar ways, which would be a prerequisite for developing a display for them. Everyone else the authors tested who had a fourth type of cone couldn't actually discriminate between colours beyond someone with the typical three types. It would be interesting to see if they gained the discrimination ability by wearing glasses with extremely narrow bandpass filters for their cones' center wavelengths, like the ones that give men with red/green colourblindness the ability to distinguish between red and green. [1] https://jov.arvojournals.org/article.aspx?articleid=2191517 https://jov.arvojournals.org/article.aspx?articleid=2191517 - which cites a much earlier paper by two of the same authors (https://pubmed.ncbi.nlm.nih.gov/8351822/ https://pubmed.ncbi.nlm.nih.gov/8351822/) that also included the subject "cDa29". [2] Search for "Simulated cone fundamentals for cDa29" in the first paper linked in [1] [3] "one participant cDa29 [...] behaves as if she has access to an additional cone signal: she made no errors at any value of (R670 / (R670 + G546)) [...] and her response times not only are faster than those of other participants [...] but are roughly even across the stimulus space"