Have you ever been tricked by an optical illusion into seeing colors that weren’t actually there? Or pondered why the infamous “the dress” photo was perceived as white and gold by some but blue and black by others? Essentially, how can colors appear different from their true nature? The answer, according to experts, lies in a complex interplay of lighting, memory, and the activity of our photoreceptor cells.
In 2015, a photograph of a dress ignited a heated debate, simply asking: What color is it? Bevil Conway, a neuroscientist and visual scientist at the National Institutes of Health in Maryland, explained, “The dress was so unusual; we don’t often have controversies about colors. We don’t disagree about white and gold or blue and black. The disagreement is about whether those colors applied to this image.” Conway and his team investigated the dilemma by asking 1,400 participants to identify the dress’s color under different lighting conditions. The findings revealed that people’s expectations of the dress’s lighting environment significantly influenced their color perception. Individuals who assumed the dress was photographed under warm or incandescent light perceived it as blue and black (its actual color). Conversely, those who assumed cool or daylight lighting saw white and gold. This demonstrates that our preconceived notions about an object’s surroundings can shape how we see its color.
Memory also plays a crucial role in our color perception. When we encounter a familiar object, our brains instinctively assign its expected hue or even enhance its color. A 2024 study further illustrated this phenomenon by asking participants to bring colored objects to the experiment. Participants were then tasked with identifying the color of these objects under various room illuminations that altered their appearance. Despite the changing lighting conditions, participants had no trouble identifying the objects’ original colors. This effect is known as color constancy. This memory-based color effect also explains why we often perceive color in the dark, even though there’s no light stimulation. Our brain likely constructs color based on our existing memories.
In contrast, when dealing with an unfamiliar object, our brains may assign color based on our expectations of what the object should look like. Akiyoshi Kitaoka, a psychologist at Ritsumeikan University in Japan, created an image of a train that appears to have a blue hue, even though it contains no blue pixels. This illusion highlights how our brains can interpret colors based on contextual clues and expectations.
Furthermore, an object’s positioning or context can make certain colors appear more intense than they truly are. For instance, a red object appears “redder” on a green background compared to a white background. This phenomenon suggests that neighboring colors can alter how we perceive specific hues.
Occasionally, our cones, the color photoreceptor cells in our retinas that convert light into brain-interpretable signals, can deceive our brains into “seeing” something that isn’t there. To illustrate, stare at a flag for 30 to 60 seconds, and then shift your gaze to a white space. Most people will observe an afterimage, a vivid image that persists after the object is removed, appearing red and blue against the white background. This occurs due to the fatigue experienced by our photoreceptors.
Most individuals possess three types of color photoreceptors, or cone cells, named according to the wavelengths they detect: long, middle, and short. Sara Patterson, a neuroscientist at the University of Washington in Seattle, explains that the “long” and “middle” cones are most effective at perceiving light within the yellow and green wavelengths of the visible spectrum. The “short” cone excels at capturing ‘lavenderish’ or violet light.
Our cone cells function like muscles and can become fatigued, Conway explains. For instance, when we focus on a red sheet of paper (which emits a long wavelength), the long cone works harder than the middle and short cones. If we then shift our gaze to a white sheet of paper, the middle and short cones will compensate for the long cone’s activity, creating the perception of a green color. This color illusion is termed a negative afterimage, or an illusion of the object’s complementary color. In contrast, the eye can also perceive an image of the same color as an object that no longer exists. This color illusion, known as a positive afterimage, typically lasts for a much shorter duration.
The same effect doesn’t manifest with a white sheet of paper because white encompasses all wavelengths within the visible light spectrum. When we observe white paper, all three types of cones are equally stimulated. Over time, the long, middle, and short cones experience fatigue to roughly the same extent.
There’s still much we don’t understand about how our brains perceive color. Patterson highlights that “where” this process occurs in the brain remains the most significant challenge. We lack a comprehensive understanding of how or which neurons are responsible for comparing the activity of cones in the retina. To make strides in understanding color perception, Conway emphasizes the need for “more productive dialogue between different branches of intellectual activity.” This includes art, philosophy, and science. Color perception is more than just a visual phenomenon, he asserts.
