How Many Colors Can Most of Us Actually See?

Derval’s article on Linkedin.com (screenshot by author for Hyperallergic, via Diana Derval/LinkedIn)

In the last few days, a LinkedIn article about differences in individual color vision by Diana Derval, president and research director of DervalResearch and self-professed “expert in neuromarketing,” has made rounds on the internet. The article, relevant in light of “The Dress” and recent questions about color perception, shows a rainbow spectrum and asks viewers how many distinct colors they are able to discern. Based on those results, Derval classifies readers into dichromats, trichromats, and tetrachromats, groups that refer to the number of cone types — color-sensitive photoreceptor cells — present in one’s retina.

Derval’s test seems to be telling a suspiciously large percentage of readers that they are tetrachromats who possess an extraordinary range of color perception. She also somehow predicts people’s color preferences. But her article cites no scholarly papers or studies, save for her own company website, and when I reached out and inquired about the studies upon which she based her conclusions, she referred me to her book The Right Sensory Mix. I took it upon myself to consult published and publicly available scientific studies in order to investigate how cones affect human vision and whether tetrachromats are as prevalent as Derval asserts.

Cones are photoreceptors on the human retina responsible for color vision. Most people are trichromatic, meaning that they have three types of cones — red, blue, and green — and information from the different types of cones combines to produce color perception. Since each type of cone enables the eye to distinguish approximately 100 shades, the average human combines those exponentially and is able to see about 1 million shades.

Evidence suggests that some people have four types of cones — including an additional orange one — and are able to see 100 million shades. According to color vision researcher Dr. Jay Neitz, only women can have four types of cones. Yet, despite the fact that up to 12% of women in the world possess four cone types, most don’t test as tetrachromatic. There are actually only 99 million women in the world with true four-color vision, according to Dr. Neitz. Based on world population estimate of 7.30 billion, that would mean only 1.36% of the world’s population has true four-color vision and can be called tetrachromats, nowhere near the 25% that Derval claims. Because the additional optical power conferred by a fourth cone is evolutionarily unnecessary, most of those with four cones never develop into true tetrachromats. In fact, in over 20 years of research, Newcastle University neuroscientist Gabriele Jordan has only come upon one true, functional tetrachromat, a doctor living in Northern England.

It is not possible to determine if one is a tetrachromat through an online test or by looking at an internet-based image because, according to the Newcastle study, “computer screens do not provide enough color information to be able to ‘tap into’ the extra dimension that tetrachromats may possess.” To verify purported tetrachromatic abilities, one would have to go to a university laboratory and undergo testing. So, despite its popular appeal, Derval’s diagram isn’t detailed or remotely accurate enough to tell much about a person’s powers of sight or color preferences.