Whether white and black count as colors depends entirely on which definition of “color” you use, and science has more than one. In physics, white is the simultaneous presence of all visible wavelengths of light, and black is the absence of light altogether. In human perception, both white and black are vivid visual experiences processed by dedicated neural pathways, making them as real as any hue your brain registers. And in pigment mixing, black and white behave as colors in their own right, absorbing or reflecting light just like red or blue paint. The question sounds simple, but it cuts across optics, neuroscience, materials science, and even linguistics, and the answer shifts depending on which field is talking.
What Physics Actually Says About White Light
Isaac Newton established in the 1670s that white light is not a single, pure thing. By passing sunlight through a glass prism, he showed that white light fans out into a continuous spread of colors, from red through violet. His key insight was to flip the conventional thinking: rather than white being fundamental and colors being modifications of it, color is the basic property, and white is a blend. Newton described light as “a heterogeneous mixture of differently refrangible rays,” meaning that each wavelength bends at a slightly different angle through glass, which is why the prism separates them.1PubMed Central. Newton shows the light: a commentary on Newton (1672) ‘A letter … containing his new theory about light and colours…’
In this framework, white is what you see when roughly the full visible spectrum hits your eye at once. Black, by contrast, is the condition in which no light (or very little) reaches your eye from a given direction. Neither white nor black occupies a single wavelength the way, say, 570-nanometer light corresponds to yellow. So from a strict optics standpoint, calling black or white a “color” in the same sense as green or orange is misleading. They don’t sit on the visible spectrum. But optics is only one lens through which to look at the question.
Your Brain Treats Black and White as Real Colors
If you’ve ever stared at a sheet of coal-black paper in a well-lit room, you know it looks actively dark, not just empty. That subjective vividness is not an illusion. Your retina has specialized neural channels for processing light increments and light decrements separately. Retinal cells called bipolar cells split incoming visual signals into ON pathways (responding to increases in light) and OFF pathways (responding to decreases), and this division is the foundation for how you perceive contrast between bright and dark surfaces.2PubMed Central. ON and OFF Signaling Pathways in the Retina and the Visual System Black is not just “nothing happening” in the visual system. The OFF pathway actively signals the presence of darkness.
Research on the specific retinal cells that feed into these pathways has shown that the midget ganglion cells, which are the most numerous type of output neuron in the human retina, sort themselves into clusters that correspond to white and black perception. ON-center midget ganglion cells serve the perception of white, while OFF-center midget ganglion cells serve the perception of black.3Frontiers in Neuroanatomy. How We See Black and White: The Role of Midget Ganglion Cells Your visual system treats brightness and darkness as parallel, active signals rather than as “signal” versus “no signal.” This is one of the strongest arguments for treating black and white as genuine perceptual colors.
The OFF pathway is remarkably sensitive. Experiments have demonstrated that OFF-type retinal ganglion cells can reliably detect tiny, quantum-level shadows even in very dim conditions, while ON-type cells tuned to light increments do not perform well in the same dim range.4Current Biology. Retinal OFF ganglion cells allow detection of quantal shadows at starlight Evolution has invested heavily in making black perceptible, which makes little sense if black were simply the absence of visual information.
Lightness Constancy and Why Your Brain Overrides Raw Light Levels
A white piece of paper in a dimly lit room and a gray piece of paper in bright sunshine can send roughly the same amount of light to your eyes, yet you effortlessly see the first as white and the second as gray. This ability, known as lightness constancy, is one of the most basic feats your visual brain performs, and it reveals something important: your perception of white and black is not a passive readout of light intensity. It is an active computation.
Neurons in the primary visual cortex adjust their responses based on the surrounding illumination, effectively factoring out lighting changes to represent the actual surface reflectance of an object. This process begins surprisingly early in the visual processing chain.5PubMed Central. Lightness constancy in primary visual cortex Further work recording from populations of neurons in both primary visual cortex and higher visual area V4 has found that groups of neurons jointly encode both the amount of light a surface reflects and the surrounding context, though exactly how the brain combines these two signals to arrive at a final perception of lightness remains an open question.6PubMed Central. Neuronal population mechanisms of lightness perception
The practical upshot: when you judge a surface as “white” or “black,” your brain is making a sophisticated inference about the surface itself, not just reporting how many photons arrived. White and black, in this sense, are perceptual categories your brain constructs. That is a strong reason to call them colors in everyday language, even if they lack a wavelength.
Lightness Illusions Show the Brain Can Be Fooled
If your brain computes white and black rather than passively detecting them, it can also get the computation wrong. Classic lightness illusions demonstrate this vividly. In the famous checkerboard shadow illusion, two squares that reflect identical amounts of light look dramatically different because one appears to sit in shadow and the other does not. Your brain “corrects” for the shadow, making the shadowed square look lighter than it physically is.
Recent work investigating what drives these illusions found that surrounding context panels are a major factor. When researchers stripped away the panels adjacent to the target squares, people’s judgments shifted toward raw brightness; when the panels were present, judgments shifted toward perceived surface lightness, showing that the brain is actively using nearby surfaces to interpret what “white” or “dark” means in a scene.7PubMed Central. Understanding the image cues driving the switch from brightness to lightness responses in the Adelson checker-block illusion Even deep learning models trained to estimate surface reflectance from images reproduce most of these illusions, suggesting they arise from something fundamental about the problem of interpreting light rather than from a quirk of biological wiring.8PubMed Central. A deep convolutional neural network trained for lightness constancy is susceptible to lightness illusions
These illusions make a useful point for the “are they colors?” question: you can be fooled about black and white in exactly the same ways you can be fooled about hue. Your brain applies the same kind of contextual processing to lightness that it applies to color, which suggests that, perceptually, they belong to the same family.
Where Classic Color Theory Gets It Wrong
For about 150 years, the dominant framework for understanding color appearance was Hering’s Opponent-Colors Theory. It proposed that all color experience can be described by three opposing pairs: red versus green, blue versus yellow, and black versus white. Under this model, black and white were built into the core architecture of color perception as one of three fundamental axes. The theory was elegant and influential, but a recent review of the accumulated evidence concludes that neither its psychological claims nor its proposed brain mechanisms hold up. The theory is, in the reviewers’ words, wrong.9Trends in Cognitive Sciences. Color appearance and the end of Hering’s Opponent-Colors Theory
That does not mean black and white are not colors. It means the tidy three-axis model that gave them a formal seat at the color table was an oversimplification. Color perception turns out to be messier and more multidimensional than Hering imagined. The black-white axis remains a genuine dimension of visual experience, but it may not operate as a simple opponent pair in the way the textbook story suggests. Older research proposed that white and black are governed by distinct visual processes, with the mechanism for white resembling the processes involved in chromatic color vision more closely than previously thought.10Vision Research. A bidimensional theory of achromatic color vision The science here is genuinely unsettled, which is itself interesting: researchers are still working out how black and white fit into the broader map of color experience.
Mixing Light Versus Mixing Paint
The confusion about whether black and white are colors often comes from conflating two very different mixing systems. In additive mixing, which is how screens and stage lights work, you start with darkness and add wavelengths. Combine red, green, and blue light at full intensity and you get white. Black is simply the starting condition when no light is emitted. In this system, white is the sum of all colors and black is zero color. A molecular-level demonstration of additive color reproduction showed that mixing ratios to produce desired color coordinates can be precisely calculated from the individual emission spectra of component molecules.11PubMed. Realizing molecular pixel system for full-color fluorescence reproduction: RGB-emitting molecular mixture free from energy transfer crosstalk
Subtractive mixing is the world of paints, inks, and dyes. Here you start with white (a surface reflecting all wavelengths) and add pigments that absorb certain wavelengths and reflect others. Mix enough pigments together and you absorb nearly everything, approaching black. The mixing behavior of real pigments follows the Kubelka-Munk model, which accounts for both how pigments absorb light and how they scatter it within a paint layer.12ACM Transactions on Graphics. Practical pigment mixing for digital painting In this system, black and white are functional endpoints. White paint and black paint are as much “colors” as any tube of cadmium red, because they behave the same way: absorbing some wavelengths and reflecting others.
So when a painter says black and white are colors and a physicist says they are not, both are correct within their own frameworks. The disagreement is about the word “color,” not about the physics or the paint.
Defining “White” for Standardized Measurement
If white is all wavelengths combined, which particular blend of wavelengths counts? Sunlight at noon is different from sunlight at sunset, which is different from a fluorescent tube. The International Commission on Illumination addressed this by defining a set of standard illuminants, each representing a different type of white light with a specific spectral distribution and a defined “white point” in color space.13RP Photonics Encyclopedia. CIE Standard Illuminants The most commonly referenced standard, known as D65, approximates average daylight including the ultraviolet component.
This matters because “white” is not one fixed thing even in physics. A piece of paper that looks perfectly white under D65 daylight can appear yellowish under incandescent light or bluish under overcast sky. The standard illuminants give scientists and engineers a shared reference so they can talk about white meaningfully without arguing about whose lamp is the “right” one. It also underscores the point that white, far from being simple, requires careful definition the moment you try to pin it down.
Engineering the Blackest Blacks and Whitest Whites
Materials scientists have pushed black and white to extremes that would have seemed impossible a few decades ago. On the black end, carbon nanotube coatings with porous microstructures can achieve average light absorption above 99.5%, meaning less than half a percent of incoming light bounces back.14Carbon. Fabrication of ultra-black carbon nanotube absorber based on hot-air assisted spray The mechanisms behind these ultra-black surfaces include light trapping in surface structures, surface plasmon effects, and bandgap engineering in semiconductors.15Laser & Photonics Reviews. Ultra‐Black Materials: Fundamentals, Design, and Applications Looking at one of these coatings in person is disorienting: three-dimensional objects coated in the material appear as flat silhouettes because your visual system has no reflected light to use for reconstructing shape or depth.
On the white end, a barium sulfate nanoparticle paint has reached a solar reflectance of about 97.6%, high enough to cool surfaces below the surrounding air temperature even in direct sunlight by reflecting nearly all incoming solar energy while efficiently radiating heat into the sky.16ACS Applied Materials & Interfaces. Ultrawhite BaSO4 Paints and Films for Remarkable Daytime Subambient Radiative Cooling An alternative approach using magnesium oxide nanoparticles in a polymer matrix has achieved about 96.3% solar reflectance with an even higher thermal emission of 98.5% in the atmospheric transmission window, making it another strong candidate for passive cooling applications.17Advanced Materials Technologies. Ultra‐Emissive MgO‐PVDF Polymer Nanocomposite Paint for Passive Daytime Radiative Cooling
These ultra-white paints are not just academic curiosities. In a warming world, coatings that reflect almost all sunlight and radiate heat back to space could meaningfully reduce air-conditioning demand in buildings and cool infrastructure. The engineering of “extreme white” has become a climate-relevant technology, which is an odd thing to say about something many people consider a non-color.
How Nature Engineers Super Black
Humans are not the only ones pushing the limits of blackness. Several species of birds of paradise produce “super black” plumage that reflects as little as 0.05 to 0.31% of incoming light, a performance that approaches human-made ultra-black coatings. The secret is not unusual pigment chemistry but microscopic structure: the feather barbules are tilted and modified in ways that cause incoming light to bounce between surfaces repeatedly, with each bounce absorbing more energy, until almost nothing escapes.18PubMed Central. Structural absorption by barbule microstructures of super black bird of paradise feathers The trait appears in at least 15 bird families, nearly always adjacent to patches of bright, saturated color, suggesting that the super black evolved to make neighboring colors look more vivid by contrast.19PubMed. Convergent evolution of super black plumage near bright color in 15 bird families
Peacock spiders use a similar trick with a different structure. Their super black patches feature brush-like scales with spiny projections that scatter light repeatedly between the spines, achieving reflectance as low as 0.77% from the scales alone.20PubMed Central. Structurally assisted super black in colourful peacock spiders At each scattering event, some light penetrates the cuticle and is absorbed by melanin pigment, while whatever reflects outward typically hits another spine and the cycle repeats. The convergence between birds and spiders is striking: two very different lineages arrived independently at the same solution of micro-scale light trapping to produce the deepest possible black.
These biological examples further complicate the “black is not a color” claim. In nature, black is an active, engineered optical feature. It is not the passive absence of something but the result of elaborate structures selected to absorb light as thoroughly as possible. Calling that “not a color” feels less like a scientific conclusion and more like an artifact of how we define the word.
Why Languages Tend to Name Black and White First
Linguists have long noticed a pattern in how the world’s languages develop color terms. Research dating back to the late 1960s, updated with modern phylogenetic methods, supports the idea that virtually every language with only two basic color terms uses those terms for black (or dark) and white (or light). A language adds terms for other hues only later, as its color vocabulary expands. A phylogenetic analysis of color term systems across many language families found broad support for this developmental sequence, while also finding that languages can lose color terms, not just gain them.21PubMed Central. Phylogenetic approach to the evolution of color term systems
The fact that black and white are universally the first color distinctions humans name suggests that the light-dark axis is the most fundamental perceptual contrast our visual systems make. Whether or not you call them “colors” in formal optics, they are the bedrock of how humans categorize the visual world. Red, blue, green, and yellow are elaborations on top of that primary division. In the history of language, at least, black and white are not secondary or derivative. They came first.
When the Answer Actually Matters
For most everyday purposes, the question is purely semantic. If you are painting a room, black and white are colors because you buy them in cans and apply them to walls. If you are calibrating a monitor, white is a target defined by a specific standard illuminant, and black is the residual light your display cannot suppress. If you are studying the retina, black and white are distinct neural signals carried by dedicated cell populations. The definition of “color” shifts to match the context, and no single answer is universally correct.
Where the distinction does matter is in fields like radiative cooling, where the difference between 96% and 98% solar reflectance translates into measurable temperature differences on building rooftops. It matters in display technology, where deeper blacks improve perceived contrast ratios and make colors appear more saturated, a trick birds of paradise figured out millions of years before screen manufacturers did. And it matters in vision science, where understanding how the brain constructs lightness from ambiguous light signals remains one of the deeper unsolved problems in neuroscience. In each of these contexts, treating black and white as mere absences or totalities misses the richness of what is actually going on.