Short answer
When the sun is low its light crosses far more atmosphere to reach you, and along that long path Rayleigh scattering strips out violet, blue and then green, leaving mainly orange and red. Dust, smoke and other aerosols change how intense and what hue the result is, and clouds lit from below take on the sun's colour.
At noon in summer, sunlight crosses the atmosphere nearly vertically. Near sunset it travels almost horizontally and passes through many times more air. The same scattering that sends blue light across the sky by day now removes blue from the direct beam before it reaches you. Violet and indigo go first, then blue, then, over the longest paths, green and yellow, leaving red as the dominant colour of the sun itself. The sky around the sun glows orange because it is lit by that depleted beam, while the sky opposite can still be blue, lit by light scattered earlier along the path.
Molecules alone would give a fairly clean orange-yellow sunset. Aerosols — dust, sea salt, wildfire smoke, volcanic sulphate — change it. Larger particles scatter more evenly across wavelengths, which dims and whitens the sun; very fine particles behave more like molecules and deepen the reddening. High, thin volcanic aerosol after major eruptions has been associated with unusually vivid, long-lasting twilight colours, while heavy smoke can turn the sun a dull red disc even at midday. So there is no single 'correct' sunset colour: it records what is in the air along a few hundred kilometres of sight line.
Clouds are the canvas. Mid- and high-level clouds stay in sunlight after the sun has set for you, and being white scatterers they take on whatever colour the reddened beam gives them, from gold to crimson. After sunset, the sky can turn pink or purple: red sunlight still illuminating the upper atmosphere combines with blue scattered skylight, and ozone absorption in the orange removes the middle of the spectrum. That later phase belongs to twilight and is covered with the blue hour.
The eye adapts continuously to the falling, reddening light, which tempers the colour you perceive; a camera with fixed daylight white balance does not, and records a more orange scene. Automatic white balance does the opposite and can neutralise the sunset altogether. Meanwhile the dynamic range between the sun's disc and the foreground is enormous, so exposure choices change the hue of clipped areas. Anyone using sunset light to judge a colour — a house exterior, a garment in a photograph — is seeing it under a strongly coloured, rapidly changing illuminant.
Why: It was judged under a strongly reddened, low-level beam that flatters warm colours.
Fix: Judge exterior colours in open shade or overcast light, then check them at the times the building is mostly seen.
Why: Fixed or automatic white balance does not reproduce the eye's partial adaptation.
Fix: Shoot raw and set white balance by eye afterwards, or bracket white balance settings.
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
FactStrong evidence
Along the long atmospheric path of a low sun, violet and indigo are scattered out first, then blue, then yellow, leaving red as the predominant colour of direct sunlight.
Source: The Color of Clouds (JetStream)
FactStrong evidence
Scattering by particles much larger than air molecules, such as cloud droplets, is almost independent of wavelength in the visible range.
Source: HyperPhysics (optics, atmospheric optics and vision pages); The Color of Clouds (JetStream)
FactStrong evidence
Near and after sunset, ozone absorption becomes a major contributor to the colour of the sky overhead.
Colourwise interpretationModerate evidence
Differences between one sunset and another are mostly differences in aerosol load along the sight line rather than in the molecular atmosphere.
Based on: Molecular Rayleigh scattering is nearly constant from day to day, whereas aerosol type and amount vary widely; follows from the scattering sources on this page.
Reviewed 29 September 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.