The color red doesn’t just light up your eyes, it sparks nearly identical patterns in your brain as it does in mine. That is the surprising claim of a new study from the University of Tübingen, where researchers showed that neural activity from one group of people could predict what color a completely different person was looking at. The work, published in the Journal of Neuroscience, suggests a universal architecture for how the human visual cortex encodes color.
Until now, neuroscientists could decode a person’s color perception from their brain scans, but only if they had data from that same brain. Michael Bannert and Andreas Bartels wanted to test whether the code was more universal. Could someone’s color be predicted without ever having studied their brain before?
“We wanted to know though how similar colors are encoded in different brains,” said Bannert. “In other words, can the colors that are seen also be deduced if we only have the neuronal color signals from the brains of other people?”
The team used functional MRI to record brain activity while volunteers looked at moving rings of color. Training a classification algorithm on the responses of one set of subjects, they then tested it on a new group. The system could still identify whether someone was seeing red, green, or yellow, even though it had never seen that individual’s chromatic responses.
The real surprise was just how consistent the results were. Subtle distinctions between shades showed up as patterned differences in visual cortex activity that held steady across brains. It wasn’t just broad categories like “red versus green” that lined up, but finer gradations as well.
“We were surprised that even the subtle differences between individual colors are so similar across brains in terms of the activity patterns they elicit,” Bartels explained.
The researchers achieved this by first mapping each person’s brain responses to black-and-white patterns, which allowed them to align the visual fields without bias from color. Once aligned, they could overlay color response data from other brains and use that template to read the new subject’s perception. It was an elegant workaround to the old problem of individual brain variation.
Why should color maps be so consistent across humans? Bartels and Bannert speculate that there may be strong functional or evolutionary pressures to keep these circuits stable. After all, reliably distinguishing ripe fruit from leaves or spotting blood against skin could be matters of survival. The patterns were also area-specific: different regions of the visual cortex handled the spatial organization of color in distinct but conserved ways.
The implications stretch beyond basic neuroscience. If brain signals can be decoded across individuals, it could open the door for communication technologies that rely less on individual calibration. It also hints at a more fundamental truth: the private world of color, long thought to be subjective, may be more shared than philosophy has allowed.
And yet, there’s an unsettling twist. If our color codes are this uniform, how much of our inner life is truly unique? That question remains unanswered, left hanging like a neon afterimage.
Journal: Journal of Neuroscience
DOI: 10.1523/JNEUROSCI.2717-20.2025
Explainer: How Do Scientists Read Colors From the Brain?
Functional MRI (fMRI) doesn’t read minds in the way sci-fi movies suggest. Instead, it measures changes in blood flow that correlate with neural activity. When people look at colors, certain visual cortex regions activate in specific patterns. By training algorithms on these patterns, researchers can “decode” which color a person is seeing. The innovation in this study was that the decoder didn’t need data from the same individual. By aligning visual field maps using black-and-white images, the scientists could apply knowledge of color signals from other brains to a new participant, and still guess the color correctly.
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Would love to know about people with partial (or complete) red-green colorblindness. How do their functional MRIs differ from those with ‘normal’ color vision?