What is colour in the context of light?

In the context of optics, color is the aspect of any object that may be described in terms of hue, lightness, and saturation. In physics, color relates to electromagnetic radiation with specific wavelengths that are visible to the human eye. This radiation makes up the visible spectrum, or light. An object's apparent color is determined by how it interacts with light. The visible spectrum spans from approximately 400 nm at the violet end to 700 nm at the red end. The eye can distinguish millions of colors through two types of light mixture: additive and subtractive. Additive mixture involves combining light beams, while subtractive mixture involves the absorption of parts of the spectrum.

How does white light split into different colours?

White light, such as sunlight, comprises various wavelengths, each perceived as a different color. When white light passes through a medium like a prism or raindrops, refraction occurs: the change in direction of a wave passing from one medium to another caused by its change in speed. This dispersion separates the light into its constituent colors because each wavelength bends at a slightly different angle. Shorter wavelengths (violet/blue) bend more than longer wavelengths (red), creating a spectrum. This is why we see rainbows, where sunlight is spread out into its colors after entering raindrops.

What is the visible spectrum?

The visible spectrum is the range of electromagnetic radiation that the human eye can perceive. It is a small portion of the total electromagnetic spectrum, with wavelengths ranging from approximately 400 nm (violet) to 700 nm (red). Within this range, different wavelengths correspond to different colors. The spectrum obtained by refracting light shows characteristic regions of color, including red, orange, yellow, green, blue, indigo, and violet. Each of these regions represents a range of individual wavelengths. Sunlight is essential for life on Earth, and the transparency of water in the visible light range is vital.

How do objects get their colour?

Objects get their color through interactions with light. Color is the aspect of an object described by hue, saturation, and lightness. An object's color arises from how it interacts with light, a form of electromagnetic radiation with specific wavelengths. When light strikes an object, some wavelengths are absorbed, while others are reflected or transmitted. The colors we see are the wavelengths that are reflected. For example, a red object absorbs most colors but reflects red wavelengths. Similarly, a blue object reflects blue light while absorbing other colors. Pigments, which are insoluble materials, in the object's surface play a key role in this selective absorption and reflection of light.

What is the difference between primary colours of light and pigment?

The primary colors of light and pigment differ because light uses additive mixing, while pigment uses subtractive mixing. Light The additive primary colors are red, green, and blue. Combining these colors in varying amounts produces almost any other color. When red, green, and blue are combined in equal amounts, white light is produced. Pigment The subtractive primary colors are cyan, magenta, and yellow. Mixing colorants, like pigments or dyes, results in subtractive color mixing through absorption and selective transmission or reflection of light.

How do human eyes and the brain perceive different colours?

The human eye distinguishes colors through specialized cells called cones in the retina . These cones contain pigments that absorb different wavelengths of light: red, green, and blue-violet. The brain interprets color based on the varying degrees to which these cones are stimulated. Visual information undergoes extensive processing in the brain, involving roughly half the cortex. Different parts of the cerebral cortex handle various image features such as color, depth, motion, and object identity. The signals from the eyes travel along the optic nerves to the lateral geniculate nuclei (LGN) in the thalamus and then to the primary visual cortex (V1) in the occipital lobe. Color perception is further processed in area V4 of the visual cortex, where cells respond to color independently of illumination.

colour

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Images & Videos

A circular RYB color wheel divided into twelve segments, showing a progression of colors from red, orange, and yellow to green, blue, and violet.

A diagram of Newton's prism experiment shows a beam of white sunlight entering a glass prism and emerging as a spread of colors labeled red, orange, yellow, green, blue, indigo, and violet.

A close up image of a digital color-picker, showing shades of greens, yellows, reds, pinks, and blues.

A palette smeared with different colors of paint sits on top of multicolored paint swatches arranged in an arch.

energy distribution in light from daylight

spectral reflectance curve of emerald green

At a Glance

$Diffraction grating$

colour summary

colour

optics

Also known as: color

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History

Top Questions

What is colour in the context of light?
In the context of optics, color is the aspect of any object that may be described in terms of hue, lightness, and saturation. In physics, color relates to electromagnetic radiation with specific wavelengths that are visible to the human eye. This radiation makes up the visible spectrum, or light.

An object's apparent color is determined by how it interacts with light. The visible spectrum spans from approximately 400 nm at the violet end to 700 nm at the red end. The eye can distinguish millions of colors through two types of light mixture: additive and subtractive. Additive mixture involves combining light beams, while subtractive mixture involves the absorption of parts of the spectrum.
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How does white light split into different colours?
White light, such as sunlight, comprises various wavelengths, each perceived as a different color. When white light passes through a medium like a prism or raindrops, refraction occurs: the change in direction of a wave passing from one medium to another caused by its change in speed.

This dispersion separates the light into its constituent colors because each wavelength bends at a slightly different angle. Shorter wavelengths (violet/blue) bend more than longer wavelengths (red), creating a spectrum. This is why we see rainbows, where sunlight is spread out into its colors after entering raindrops.
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What is the visible spectrum?
The visible spectrum is the range of electromagnetic radiation that the human eye can perceive. It is a small portion of the total electromagnetic spectrum, with wavelengths ranging from approximately 400 nm (violet) to 700 nm (red).

Within this range, different wavelengths correspond to different colors. The spectrum obtained by refracting light shows characteristic regions of color, including red, orange, yellow, green, blue, indigo, and violet. Each of these regions represents a range of individual wavelengths. Sunlight is essential for life on Earth, and the transparency of water in the visible light range is vital.
3 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How do objects get their colour?
Objects get their color through interactions with light. Color is the aspect of an object described by hue, saturation, and lightness.

An object's color arises from how it interacts with light, a form of electromagnetic radiation with specific wavelengths. When light strikes an object, some wavelengths are absorbed, while others are reflected or transmitted. The colors we see are the wavelengths that are reflected.

For example, a red object absorbs most colors but reflects red wavelengths. Similarly, a blue object reflects blue light while absorbing other colors. Pigments, which are insoluble materials, in the object's surface play a key role in this selective absorption and reflection of light.
4 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What is the difference between primary colours of light and pigment?
The primary colors of light and pigment differ because light uses additive mixing, while pigment uses subtractive mixing.

Light

The additive primary colors are red, green, and blue. Combining these colors in varying amounts produces almost any other color. When red, green, and blue are combined in equal amounts, white light is produced.

Pigment

The subtractive primary colors are cyan, magenta, and yellow. Mixing colorants, like pigments or dyes, results in subtractive color mixing through absorption and selective transmission or reflection of light.
3 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How do human eyes and the brain perceive different colours?
The human eye distinguishes colors through specialized cells called cones in the retina. These cones contain pigments that absorb different wavelengths of light: red, green, and blue-violet. The brain interprets color based on the varying degrees to which these cones are stimulated.

Visual information undergoes extensive processing in the brain, involving roughly half the cortex. Different parts of the cerebral cortex handle various image features such as color, depth, motion, and object identity. The signals from the eyes travel along the optic nerves to the lateral geniculate nuclei (LGN) in the thalamus and then to the primary visual cortex (V1) in the occipital lobe. Color perception is further processed in area V4 of the visual cortex, where cells respond to color independently of illumination.
5 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

colour, the aspect of any object that may be described in terms of hue, lightness, and saturation. In physics, colour is associated specifically with electromagnetic radiation of a certain range of wavelengths visible to the human eye. Radiation of such wavelengths constitutes that portion of the electromagnetic spectrum known as the visible spectrum—i.e., light.

Vision is obviously involved in the perception of colour. A person can see in dim light, however, without being able to distinguish colours. Only when more light is present do colours appear. Light of some critical intensity, therefore, is also necessary for colour perception. Finally, the manner in which the brain responds to visual stimuli must also be considered. Even under identical conditions, the same object may appear red to one observer and orange to another. Clearly, the perception of colour depends on vision, light, and individual interpretation, and an understanding of colour involves physics, physiology, and psychology.

An object appears coloured because of the way it interacts with light. The analysis of this interaction and the factors that determine it are the concerns of the physics of colour. The physiology of colour involves the eye’s and the brain’s responses to light and the sensory data they produce. The psychology of colour is invoked when the mind processes visual data, compares it with information stored in memory, and interprets it as colour.

This article concentrates on the physics of colour. For an overview of the primary colours, with their basic secondary and tertiary mixtures, usefully notated as the 12 segments of a circle, see colour wheel. For a discussion of colour as a quality of light, see light and electromagnetic radiation. For the physiological aspects of colour vision, see eye: Colour vision. See also painting for a discussion of the psychological and aesthetic uses of colour.

Colour and light

The nature of colour

Aristotle viewed colour to be the product of a mixture of white and black, and this was the prevailing belief until 1666, when Isaac Newton’s prism experiments provided the scientific basis for the understanding of colour. Newton showed that a prism could break up white light into a range of colours, which he called the spectrum (see figure), and that the recombination of these spectral colours re-created the white light. Although he recognized that the spectrum was continuous, Newton used the seven colour names red, orange, yellow, green, blue, indigo, and violet for segments of the spectrum by analogy with the seven notes of the musical scale.

Artist paint brushes and watercolor paintbox on wooden palette. Instruments and tools for creative leisure. Creative background. Paintings art concept. Painting hobby. Back to school. Top view.

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More Art and Colors Quiz

Newton realized that colours other than those in the spectral sequence do exist, but he noted that

all the colours in the universe which are made by light, and depend not on the power of imagination, are either the colours of homogeneal lights [i.e., spectral colours], or compounded of these.

Newton also recognized that

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rays, to speak properly, are not coloured. In them there is nothing else than a certain power…to stir up a sensation of this or that colour.

The unexpected difference between light perception and sound perception clarifies this curious aspect of colour. When beams of light of different colours, such as red and yellow, are projected together onto a white surface in equal amounts, the resulting perception of the eye signals a single colour (in this case, orange) to the brain, a signal that may be identical to that produced by a single beam of light. When, however, two musical tones are sounded simultaneously, the individual tones can still be easily discerned; the sound produced by a combination of tones is never identical to that of a single tone. A tone is the result of a specific sound wave, but a colour can be the result of a single light beam or a combination of any number of light beams.

A colour can, however, be precisely specified by its hue, saturation, and brightness—three attributes sufficient to distinguish it from all other possible perceived colours. The hue is that aspect of colour usually associated with terms such as red, orange, yellow, and so forth. Saturation (also known as chroma or tone) refers to relative purity. When a pure, vivid, strong shade of red is mixed with a variable amount of white, weaker or paler reds are produced, each having the same hue but a different saturation. These paler colours are called unsaturated colours. Finally, light of any given combination of hue and saturation can have a variable brightness (also called intensity or value), which depends on the total amount of light energy present.

colour

Light

Pigment

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Colour and light

The nature of colour