On the fabulous planet that we call Earth, there are very few animals that can change colour rapidly, be it for camouflage, intraspecies signalling, or thermal regulation. One of these animals is chameleons, of course! While this behaviour is a widely known fact, less is known about the peculiar science of how these creatures change their scales in an instant, and why they undergo this strange phenomenon.
How do chameleons change colour?
It all begins with the most basic unit of life: cells. In the skins of chameleons are chromatophores, which are cells that give chameleons their dynamic and vibrant hues. Chromatophore cells can be split into two groups:
1. Pigment-producing chromatophores: these secrete–you guessed it!–pigments, which absorb specific wavelengths of light, and
2. structural chromatophores: these reflect and scatter light (1).
You might remember from high school physics that each colour of light has a different wavelength. Following this principle, each chromatophore selectively absorbs and reflects specific wavelengths (colours) of light, allowing chameleons to display different colours at different times at will. For instance, when a chameleon appears green, it is reflecting light with a wavelength between 510-565 nanometres (2).
Pigment Chromatophores
In chameleons, melanophores are pigment chromatophores that produce the black-brown pigment called eumelanin (3). You and I also have eumelanin in our pigment cells, in addition to the yellow-red pigment pheomelanin (1), which gives rise to red-coloured hair in humans (4).
Some more types of pigment chromatophore in chameleons are the erythrophores and xanthophores (1), which both contain the pigments called carotenoid and pteridine, but in different proportions (3). Erythrophores have a higher ratio of carotenoid pigment and thus appear red, while xanthophores have more pteridine and hence appear yellow (5).
Pigment-producing chromatophores possess long, thin, arm-like protrusions called dendrites. Pigment can be dispersed to these appendages or remain aggregated in the cell centre, changing the colour of the cell and, on a larger scale, the appearance of the chameleon. For example, when eumelanin in melanocytes is dispersed along these dendrites, the cells will appear light in colour, while concentration of eumelanin at the cell’s centre gives the chameleon a darker appearance (6). The image below demonstrates how pigment is dispersed and aggregated in frog and fish melanophores specifically, although chameleon melanophore cells have the same function.
Structural Chromatophores
Iridophores are different from pigment chromatophores in the way that they reflect light (1). Iridophores contain purine crystal lattices (3) arranged into thin platelets with spaces between them (7). These gaps reflect and scatter light to create iridescence, sort of like a mirror (7). Thus, structural chromatophores use physical structures to reflect light while pigment-producing chromatophores use chemicals (pigments) to reflect light. Incidentally, iridophores are the only type of structural chromatophore present in chameleons (1).
When all four types of chromatophores mature, they create associations with each other and interconnect to form a “dermal chromatophore unit.” Located below the epidermis of the chameleon skin, the dermal chromatophore unit is what ultimately manipulates the colour of chameleon, as all cells undergo coordinated pigment reorganisation (1). This is a process known as metachrosis (8).
Coordination of the chromatophores to colour the chameleons is regulated by the nervous system and the endocrine system. The release of hormones and neurotransmitters can regulate whether the pigment molecules are aggregated at the centre of the chromatophores, or if they are dispersed to the dendrites (1).
Why do chameleons change colour?
The predominant theories behind the dynamic colouring of chameleons are crypsis (camouflage) and social signalling (9).
Chameleons undergo metachrosis to camouflage into their surroundings to avoid predation. There is evidence that chameleons have predator-specific colourations. For example, dwarf chameleons (genus Bradypodion) will more effectively match their environments if they are being preyed on by a bird than if they are being hunted by a snake. A reason for this could be that birds have better colour vision than snakes, so chameleons won’t waste their energy on costly, high-precision disguises unless necessary (10).
However, contrary to popular belief about camouflaging chameleons, in some species, camouflage is only a minor part of their evolution! Instead, colour-change plays a major role in social signalling. One of the main types of social signalling that male chameleons utilise is displaying a variety of colours, both for asserting dominance and courting females. Vibrant colours (such as bright orange) are typically associated with dominance. Interestingly, males who lose a fight or are rejected often showcase species-specific submissive colouration, which is often brown (9).
But what about female chameleons? In some cases, females can use colour patterns to signal reproductive status, although this is uncommon (9).
Another reason for metachrosis is thermoregulation. As an ectothermic animal (or, colloquially, a cold-blooded animal), chameleons use the sun to maintain their body temperature. Thus, chameleons will take on a uniformly dark body to maximise solar absorption to warm up when in the sun, and once they have reached optimum thermal temperature, they will take on a lighter colouration (11).
Interestingly, metachrosis is common in other animals, particularly cold-blooded species, such as iguanas, lizards, and even amphibians (8). All of these animals use their chromatophores in similar ways to chameleons. So hopefully next time you are at a zoo or out in nature and see an animal with vibrant colours, you will remember exactly how they have adapted to the world around them!
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References'
Ligon RA, McCartney KL. Biochemical regulation of pigment motility in vertebrate chromatophores: a review of physiological color change mechanisms. Curr Zool. 2016;62(3):237-252. doi:10.1093/cz/zow051.
Klein RM. Effects of green light on biological systems. Biol Rev Camb Philos Soc. 1992;67(2):199-284. doi:10.1111/j.1469-185X.1992.tb01019.x.
Visconti MA. Editorial: Color change: neural and hormonal control of pigmentation. Front Endocrinol (Lausanne). 2024;15:1476470. doi:10.3389/fendo.2024.1476470.
Schlessinger DI, Rahimi N, Schlessinger J. Biochemistry, melanin. StatPearls. January, 2025. Updated July 14, 2025. Accessed August 29, 2026. https://www.ncbi.nlm.nih.gov/books/NBK459156/
Bagnara JT. Cytology and cytophysiology of non-melanophore pigment cells. International Review of Cytology. 1966;20:173-205. doi:10.1016/S0074-7696(08)60801-3.
Alexander I. Melanophores with dispersed or aggregated melanosomes [Internet]. Wikimedia Commons; 2012 Nov 27 [cited 2026 Aug 29]. Available from: https://commons.wikimedia.org/wiki/File:Melanophores_with_dispersed_or_aggregated_melanosomes.jpg
Morrison RL. The biology of iridophores in reptiles [Internet]. University of Kansas; 1993 May 31 [cited 2026 Oct 4]. Available from: https://kuscholarworks.ku.edu/entities/publication/c1a43a61-6ebe-48f7-b42c-8588b8c6310f
Stonedale N, Patrick P. The role of metachrosis in thermoregulation of Sceloporus malachiticus. Monteverde Institute: Tropical Ecology and Conservation; 2003 Dec [cited 2026 Oct 4]. Available from: https://digitalcommons.usf.edu/tropical_ecology/615/
Stuart-Fox D, Moussalli A. Selection for social signalling drives the evolution of chameleon colour change. PLoS Biol. 2008;6(1). doi:10.1371/journal.pbio.0060025.
Stuart-Fox D, Moussalli A. Camouflage, communication and thermoregulation: lessons from colour changing organisms. Philos Trans R Soc Lond B Biol Sci. 2009;364(1516):463-470. doi:10.1098/rstb.2008.0254.
Bennett AF. Thermoregulation in African chameleons. Int Congr Ser. 2004;1275:234-241. doi:10.1016/j.ics.2004.09.035.
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