alt Hacker News> The magic number to remember is the "Just Noticeable Difference" (JND). For dE00, JND is around 2.0. Below that, people struggle to tell two colours apart. Below 1.0, basically no one can.
Except for a tetrachromat. Specifically, a strong tetrachromat that has both four colour channels in the brain and a different frequency on the fourth cone.
Who are, admittedly, hella rare. Apparently there are less than a few dozen confirmed world-wide.
But they do exist.
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snarkconjecture • today at 10:12 AM
Computer screens have three-dimensional color spaces. Tetrachromacy doesn't change that.
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> admittedly, hella rare. Apparently there are less than a few dozen confirmed world-wide
What's actually hella rare is tests for tetrachromacy. Given the total number of people who have ever taken such a test, I think it's reasonable to assume there are significantly more than a few dozen actual tetrachromats out there.