Colour can be a physical structure, not just a pigment
Most of us assume colour comes from pigments, the coloured chemicals in paint, ink, or feathers. But there is a second route: structural colour, where colour arises from the way light interacts with regularly arranged physical structures, producing colour through completely different optical mechanisms than dyes and pigments [1]. The same idea explains why a soap bubble or a peacock feather can shift hue as you move: the geometry, not the chemistry, is doing the work.
Structural colour is found throughout the tree of life, but as of this overview it had not been reported in the true fungi [1]. That absence is itself informative. It tells us that colour as a physical phenomenon is real and widespread, yet its distribution across living things is uneven and still being mapped. The paper's aim was to stimulate a search for the phenomenon in fungi, which means the question of where structural colour exists is an open empirical one, not a settled fact [1].
Some colour exists as a chemical state that can be turned on and off
A third sense of colour is chemical and dynamic. In spiropyrans, molecules exist in solution as an equilibrium mixture of two forms: a colourless modification and a coloured one, with temperature and polar solvents favouring the coloured form [3]. This is colour as a state a substance can occupy, not a fixed label attached to an object.
That matters for the question because it shows colour existing in a measurable, reversible way inside ordinary chemistry. The coloured modification is not an illusion or a convention; it is a form the molecule takes under particular conditions [3]. So when someone asks whether colour exists, part of the answer is that certain materials genuinely have coloured and colourless states, and which one you see depends on the conditions around them.
Colour also exists in minds, languages, and cultures
Colour is not only out there in light and matter; it is also something perceivers do. One account describes colour and shape as inseparable elements of human optical perception, and argues that colour exists both in the external, objective world of reality and in the inner, subjective world of people, where it generates emotional and psychological effects [5]. On this view, colour is a complex, many-sided perception rather than a simple sensation, tied to physiological, psychological, and cultural-social factors [5].
Language adds another layer. Work on basic colour terms treats colour as a paradigmatic example, not of the relativity of semantic structures, but of the existence of something shared across highly differentiated systems of colour categories [2]. In plain terms, languages carve up colour differently, yet the fact that they all have colour categories at all suggests something real is being categorized. The categories vary; the phenomenon they encode does not simply dissolve.
Philosophy pushes on the same tension from another direction. One treatment notes that sensory experiences of colour can and do exist whether or not their subjects are actually seeing anything coloured, while also observing that many colour scientists and some philosophers hold that colours, as commonly conceived, cannot be real properties of the world [4]. That is not a debunking of colour so much as a warning that "colour exists" can mean "colour experience exists" or "coloured properties exist," and those are different claims.
So which colour are you asking about?
Putting the pieces together, the honest answer is layered. Colour exists as physical structure in living things, though its presence in true fungi was, at the time of that overview, unreported [1]. It exists as a chemical state that materials can enter and leave [3]. It exists as perception and as a near-universal target of linguistic categorization, even where the categories differ [2][5]. And it exists as experience even in cases where philosophers dispute whether coloured properties themselves are real [4].
The practical upshot for a curious reader: don't ask whether colour is real in general. Ask whether the colour you mean is in the light and structure, in the chemistry, in the eye and brain, or in the words a culture uses. Each of those has evidence behind it, and each answers a slightly different question.
Sources used in this answer
Does Structural Color Exist in True Fungi?
Structural colour, which arises from light interacting with regular physical structures rather than pigments, is widespread across the tree of life but had not been reported in true fungi, and the authors call for a search for it there.
The linguistic significance of the meanings of basic color terms
Basic colour terms are treated as evidence for the existence of shared colour categories across highly differentiated linguistic systems, rather than as evidence of pure semantic relativity.
PHOTOCHROMISM IN SPIROPYRANS. PART IV.1 EVIDENCE FOR THE EXISTENCE OF SEVERAL FORMS OF THE COLORED MODIFICATION
Spiropyrans in solution exist as an equilibrium between a colourless form and a coloured form, with temperature and polar solvents favouring the coloured modification.
Consciousness, color, and content
Colour experiences can exist whether or not their subjects are perceiving anything coloured, while many colour scientists and some philosophers hold that colours as commonly conceived cannot be real properties.
THE SYMBOLIC AND PSYCHOSEMANTIC POLYVALENCE OF COLORS
Colour is argued to exist both in the external objective world and in the inner subjective world of perceivers, shaped by physiological, psychological, and cultural-social factors.