Tetrachromacy Test: Can You Really See 100 Million Colors?

Every few months the same image resurfaces on social media: a band of color gradients with a caption asking, "How many colors can you count?" The rules are always the same — if you count more than some magic number (usually 32 or 39), congratulations, you might be a tetrachromat, blessed with a rare fourth cone that unlocks a hidden dimension of color.

It first took off on LinkedIn, posted by someone presenting themselves as a researcher, and has since gone viral again and again across TikTok, Instagram, and BuzzFeed quizzes. It spreads so well because it offers an irresistible promise: you might have a secret superpower, and you can "prove" it just by counting colors.

Here is the buzzkill that happens to be true: no online image can test for tetrachromacy. Not because the tests aren't good enough, but because screens physically cannot do it. Here's why — and what tetrachromacy actually is.

Most people are trichromats: the retina has three types of cone cell, most sensitive to long (red), medium (green), and short (blue) wavelengths. The brain combines these three signals to let us distinguish roughly one million shades.

A tetrachromat has a fourth functional cone, usually peaking somewhere between red and green. In theory, that extra dimension of information could push the number of distinguishable colors up to around 100 million. Note the words "in theory" — that figure is extrapolated from the math of cone types, not something anyone has counted out.

The crucial catch: carrying the gene for a fourth cone and actually using it to see more colors are two different things. Studies estimate up to 12% of women may carry the relevant genetic variant, but only a tiny fraction show genuinely enhanced color discrimination under rigorous lab testing. The vast majority of carriers see the world exactly as an ordinary trichromat does.

This is the heart of the matter, and the part nearly every viral quiz skips. Your screen — phone, laptop, or 4K monitor — emits light using just three primary colors: red, green, and blue. Every color it shows you is those three lights mixed in different ratios.

A tetrachromat's advantage is precisely the ability to distinguish wavelength combinations that a three-primary system cannot reproduce. In other words, the physical information that would let a tetrachromat see extra colors simply isn't present in the light coming off your screen. Even if you genuinely were a tetrachromat, you'd see the same restricted gamut as a trichromat when looking at a display.

So what does the "count the shades" image actually measure? It measures your screen's tonal resolution and your room's lighting, plus a little ordinary variation in normal color vision. Change the brightness or your viewing angle and your count changes. It's not a test of your eyes; it's a test of your monitor.

The genes for the red and green cone pigments sit on the X chromosome. Women have two X chromosomes, so they can carry a slightly different version of the red or green cone gene on each one — exactly the setup needed to produce a fourth cone type.

Men have only one X chromosome and no second copy to differ from, which means men cannot be functional tetrachromats. Intriguingly, the same X-linked inheritance explains why red-green color blindness is far more common in men — two sides of the same coin. For the full inheritance logic, see our genetics of color blindness guide.

Here's the satisfying twist: while you can't test for super-vision online, you can reasonably screen for the opposite — color blindness. The reason is the same one from above: color blindness involves color confusions that a three-primary screen can reproduce.

• • Ishihara plates: the classic "number hidden in the dots" test, a fast screen for red-green deficiency. Take the Ishihara test.
• • Red-green test: targets the specific confusion axis directly. Red-green test.
• • Hue arrangement tests: the Farnsworth D-15 and Munsell 100 Hue measure how finely you can order shades. Try the D-15.
• • Color vision simulator: want to see what the world looks like with different deficiencies? Open the simulator.

None of these will tell you you're a tetrachromat, but they give you a real picture of your everyday color discrimination — which is far more useful than an impossible superpower quiz.

Tetrachromacy is real and genuinely fascinating — but it's vanishingly rare, limited to women, and cannot be proven by an image on a screen. The next time "how many colors can you see" floods your feed, have fun with it, but don't treat it as a diagnosis. It's measuring your monitor, not your retina.

If you're genuinely curious about your color vision, the answer is within reach — just in the opposite direction: a validated color blindness screen, on a screen that can render it fairly, to learn what your color discrimination is actually like.