Two people stand in front of the same poster and do not see the same image. One sees a red field next to a green one, while the other sees two shades of the same yellow-brown tone. A third has a lens that has yellowed over seventy years and perceives blue less vividly than she did at twenty. This article is about what research actually knows about how differently we see color, and what that means when you choose an image - for yourself or someone else.
Quick facts: Red-green color weakness affects about 8 percent of boys but less than 1 percent of girls, according to Jan Ygge, professor emeritus of ophthalmology, in Karolinska Institutet’s Ask the Researcher service. Sophie Wuerger at the University of Liverpool tested 185 people between the ages of 18 and 75 (PLoS ONE, May 8, 2013) and found that the ability to distinguish small color differences declines with age, most notably along the blue-yellow axis. Claude Monet was diagnosed with cataracts in 1912, at the age of 72, and underwent surgery in January 1923.
Eight percent of boys: why color weakness is inherited on the X chromosome
The statistic comes from Jan Ygge, who prefers the term color weakness to color blindness in Karolinska Institutet’s popular science Q&A column. True color blindness, where the world consists only of shades of gray, is extremely rare, according to him. What affects one in twelve boys is something else: the three types of cones in the retina do not function in the same way, making it difficult to distinguish red from green. In a class of twenty-five boys, that means two on average.
The explanation lies in the X chromosome. Patrik Magnusson, a researcher at Karolinska Institutet and head of the Swedish Twin Registry, describes the condition as a genetically determined variation inherited recessively via the X chromosome. Boys have only one X chromosome and no backup. Girls almost always have a healthy second X chromosome that compensates. That is why the pattern is so skewed between the sexes. According to 1177, the blue-yellow variant does not follow sex in the same way and is much rarer.
Magnusson also highlights something fascinating: identical twins can differ. This may be because their cones developed differently before birth, or because the faulty X chromosome is active in one twin and the healthy one in the other. In other words, color vision is not just a matter of genes, but also of how their instructions happened to be interpreted during fetal development.
Healthcare is quite straightforward about what this means in everyday life. Congenital color vision deficiency cannot be treated, but most people who have it rarely notice any problems. Assessment is done using color plates with dots, one eye at a time, with about ten seconds per image. The whole test takes five to ten minutes. What such a test does not tell you is how you perceive the red painting above the sofa, and this is where interior design becomes interesting. A motif featuring a red flower against green foliage may blend together for some people if the two tones have the same brightness. Read more about how color affects us in other ways in our overview of the psychology of color.
The yellowing lens: Wuerger's study on color vision between the ages of 18 and 75
You don't have to be born with color vision deficiency to see color differently. The eye's lens gradually yellows with age and acts as a faint yellow filter that lets through less short-wavelength blue light. Sophie Wuerger, of the Department of Psychology at the University of Liverpool, wanted to know what this does to color perception in everyday life. Her study, published in PLoS ONE on May 8, 2013, included 185 people with normal color vision, 82 men and 103 women, aged 18 to 75, with an average age of just over 34.
The result is more nuanced than the headlines one might expect. In daylight, only the perception of pure green actually shifts with age, and the shift is smaller than the lens model predicts. The author concludes that the brain compensates for the yellowing lens, probably in the cerebral cortex, so that a white sheet of paper continues to look white to a seventy-year-old. So we do not go around in an ever-yellowing world.
What does decline, however, is the ability to distinguish small differences in color. Sensitivity decreased noticeably with age along all three tested axes, and the decline was most pronounced along the blue-yellow axis, entirely in line with the reduced amount of blue light. Two subtle shades, such as light blue and light green, are therefore more likely to blend together for an older eye than for a young one.
"A poster has no color of its own - color emerges only through the interaction of the pigment, the light, and your retina."
For anyone choosing art for parents or grandparents, this is a practical insight. A motif built on subtle, tone-on-tone contrasts can be lost. A motif with a clear difference in brightness between the figure and the background can be seen by everyone. The same principle applies to all eyes, but it matters more as we get older.
Monet’s cataracts: when a painter’s palette follows the eye’s decline
The most famous illustration of how vision shapes art is Claude Monet. His vision problems began in 1907, cataracts were detected in 1908, and in 1912 he was diagnosed with bilateral cataracts, worst in the right eye. He was 72 at the time. He put off treatment for a decade. By 1922, his right eye could only perceive light, and his left had one-tenth of normal visual acuity.
As the cataracts matured, his palette changed. The brushstrokes grew coarser, the outlines blurrier, and the colors shifted toward red and brown, which is what a yellowed, clouded lens does to light. In January 1923, he was operated on by Dr. Charles Coutela, in several stages that continued until July of that year, when the posterior lens capsule was removed at his home in Giverny. Afterward, everything seemed too yellow to him, a condition known as xanthopsia. By the summer of 1924, blue had replaced yellow as his dominant color. Explanations differ: either it was due to the removed lens, or because he gained access to ultraviolet light that an ordinary lens blocks.
The operation was no easy fix. He developed double vision and distorted shapes, struggled with depression, and eventually got help from glasses with special Zeiss lenses. In the meantime, he continued working on the large water-lily panels for the Orangerie. He died on December 5, 1926. All this makes his late work a record of how vision affects what is painted. To read about the anniversary and the Orangerie, see our article on Monet 100 years, and the works can be found in our collection of paintings and posters by Claude Monet.
The fourth cone: tetrachromats who may see one hundred million colors
Can it go the other way? Can someone see more than the rest of us? The idea was first put forward in 1948 by the Dutch researcher H.L. de Vries. Most people have three kinds of cones, but women who carry a variant of the genes for color deficiency may have a fourth, slightly shifted type. John Mollon at Cambridge began looking for such women in the 1980s and estimated that around twelve percent of all women should have the extra cone. However, his own early tests showed nothing: the women saw the same colors as everyone else.
It was Gabriele Jordan at Newcastle University who went further. She tested 25 women with a fourth cone, and one of them, known as cDa29, could distinguish three colored lights in every trial that everyone else perceived as identical. She is estimated to see up to around one hundred million colors, compared with roughly one million for an ordinary trichromat. Caution is warranted: only one person has been confirmed so clearly, the figures are rough, and it is still unclear what enables someone to actually make use of the fourth cone. Researcher Jay Neitz has suggested that it may require practice and specially designed colors.
The point for those of us who hang art isn't that everyone should seek superhuman eyes, but to remember that color lives in the brain, not in the print. The same pigment creates different experiences in different minds, and that's one reason art speaks differently to different people.
How to choose a poster that works for many kinds of eyes
Research points to a few practical rules of thumb. The first is about brightness. Let the image rely on differences in brightness, not just differences in color, so everyone can make out the figure. Black-and-white images are the purest option, since the entire image is made up of brightness. In our selection of black-and-white posters, you'll find images that look the same regardless of which cones you have and how old your lens is.
The second is about color pairings. Red against green is the classic case where two shades of the same brightness can blend together for someone with red-green color vision deficiency. Blue against orange, on the other hand, usually remains distinct, which is why it's often used in color-safe diagrams. The third is about age: because the ability to distinguish colors along the blue-yellow axis declines, pale blue and pale yellow against a pale green background should be avoided as the main subject for an older person. Choose clear shapes and stronger contrasts, like in graphic posters where lines and fields stand out against each other.
Tip: Photograph the image on your screen with your phone camera and set the filter to black and white. If you can still tell the figures apart, the image has enough contrast in brightness to work even for eyes that can't distinguish red from green, or are over seventy years old.
The fourth is about light. The same poster looks different in morning light and under an evening lamp, as we discussed in the article about how light changes art on the wall. Combine age-related sensitivity to blue with a warm lamp, and blue tones become even fainter. In that case, it helps to choose a light source with a high color rendering index.
The fifth rule is not to guess. Don't describe a gift as having that lovely shade of green if you don't know how the recipient sees. Instead, ask what shapes and moods they like. And if you have color vision deficiency yourself, ask someone you trust to look at the image, or choose based on brightness, subject matter, and composition rather than color.
Frequently asked questions about color vision and posters
Research on color vision does something unexpected to the choice of art: it dispels the illusion that we all see the same thing. If you want to find a design that works for different eyes and in different lighting, a good place to start is our posters. Choose clear shapes and contrasts, and let the person who’ll receive it take a look first. To explore the research further, see Karolinska Institutet, Wuerger’s study on color constancy throughout life, and Hektoen International’s article on Monet’s cataracts.