Because the magic system of my Lightbringer Series is intensely concerned with color and perception, and because I treat these in a mostly scientific fashion, I tend to get a lot of emails from readers pointing out the latest BuzzFeed or whatever quiz. “This woman can see millions more colors than the average person! Can you?” Or, “Are you a tetrachromat? Take this test and see!”
This link explains why most of those are complete garbage. And my thanks to Unreasonably Dangerous Onion Rings for taking the time to debunk this so that I could spend my time writing novels.
The TL;DR: It is physically impossible for these tests to tell if you a functional 4th cone because computer monitors make their colors by mixing only 3 colors, RGB.
This is not to say that all the information or all the quizzes on the internet are worthless. Ones like this are very interesting http://www.xrite.com/online-color-test-challenge, but still limited by the quality of your computer monitor, and how well you’ve calibrated it. So comparing your score to someone else’s is almost meaningless, unless you were both using the same computer. (Naturally, I got a perfect score.)
Or things like this are really closer to astrology, but are fun nonetheless: http://www.astro.com/cgi/atxgen.cgi?btyp=cf and the Lüscher Color Test: http://www.luscher-color.com/ is significantly more scientific from what I can tell, and is used as psychological diagnostic tool. But either to protect their intellectual property, or because of the flaws of RGB screens, it is only available in physical form. I’ve taken the test. Very interesting.
Sidenote for my own readers: in my world, I have 50% of women be tetrachromats. In the real world, it’s possible that 12% of women are tetrachromats. And most of those non-functionally tetrachromatic, because they’re never taught how to even distinguish those extra colors. I use this 1) there would be a competitive advantage for such women in a world with the kind of magic mine has and 2) because it makes for better fiction. It is genetically possible, though incredibly rare, for tetrachromacy to occur in men. It would, however, usually come with other unpleasant disabilities which I chose to elide. This series is reality-heavy as it is.
P.S. It’s totally fine to tag me when you find cool color stuff online. I most likely have already seen it, but it may be a new discovery, I certainly don’t mind when people tag me on things I’ve seen a dozen times, so don’t worry about it!