Short answer
Most often because the scene was lit by fluorescent tubes or low-quality LEDs, whose light carries a green excess the camera did not fully remove; green light bouncing off grass, trees or walls, and auto white balance misreading a green-heavy scene, are the other usual causes. Whether the cast covers the whole frame or only part of it tells you which.
1. Fluorescent or low-quality LED lighting with a green spike
Test: Take one photo under the room lights and one of the same subject by a window with the room lights off. If only the indoor one is green, the light source is responsible.
Fluorescent tubes emit a strong green mercury line, and some cheap LEDs sit above the black-body line; the camera's white balance may not correct either fully.
2. Green surroundings reflecting onto the subject
Test: Look at what is near the subject: grass, foliage, green walls or a green umbrella. Move the subject away or cover the green surface with a white sheet and shoot again.
Light bouncing off large green surfaces is green; skin in the shade of trees picks it up.
3. Auto white balance guessed wrong
Test: Photograph a sheet of white paper in the same light. If the paper looks green in the photo, set white balance from it (or from a grey card) and reshoot.
Auto white balance cannot always tell a green light from a green scene, especially when a large green area fills the frame.
4. Mixed light sources in one frame
Test: Check whether only part of the image is green — for example the area lit by overhead tubes while window light elsewhere looks normal.
White balance corrects one light colour at a time; the second source keeps its cast.
Causes are ordered by how often Colourwise expects each to be the explanation — an editorial judgement, so test them all.
Where the green sits is the best clue. A cast across the entire image, including whites and greys, means the light or the white-balance setting was wrong for the whole scene; one click on a neutral area in any editor usually removes it. A cast in only part of the frame — the side lit by overhead tubes while window light elsewhere looks normal — means mixed light, which no single white-balance setting can fix. A cast only on faces, necks and the undersides of objects, with whites looking fine, means green light reflected from nearby foliage, grass or painted walls. Each of these needs a different response, and the photography topics on white balance and mixed lighting cover the mechanisms.
Fluorescent tubes contain mercury, whose emission includes a strong line in the green at 546 nm on top of the phosphor glow. Eyes adapt to it and call the room white; cameras record the excess, and automatic white balance does not always remove all of it, especially when the frame is dominated by one colour or the light is dim. Some inexpensive LED lamps have a white that sits slightly on the green side of neutral with a similar result. The quickest test is two photos of the same subject, one under the room lights and one by a window with the room lights off. If only the indoor one is green, the light is responsible.
Photographers working under fluorescent light traditionally put a magenta 'plus-green' correction filter on the flash, so flash and room light have the same green excess and one white-balance setting fixes both.
Light that reaches a subject after bouncing off a lawn, a hedge, a tree canopy or a green-painted wall has been filtered by those surfaces and arrives green. In open shade under trees, much of the light on a face is exactly this. White balance cannot correct it cleanly, because the rest of the scene is lit differently and a correction that neutralises the skin shifts everything else towards magenta. The fixes are physical: move the subject out from under the canopy, put a white reflector or sheet on the side facing the green, or add a little flash. In editing, a local adjustment on the affected area is more successful than a global one.
For a whole-frame cast, set white balance from something known to be neutral: a grey card or a sheet of white paper photographed in the same light is ideal, and any white or grey object in the scene is the next best. Camera white balance works by scaling the red, green and blue channels so that neutrals come out neutral, and it can do that for only one light colour at a time. Shooting raw lets you make the correction afterwards without loss; JPEGs tolerate small corrections but degrade with large ones. For mixed light, correct for the dominant source and then fix the rest locally, or turn off one source and reshoot — matching lights before shooting beats repairing afterwards.
Why: The green came from local reflection, not the main light
Fix: Use a local adjustment on the face, or reshoot with a white reflector on the green side
Why: Fluorescent green excess that auto white balance only partly removes
Fix: Set a custom white balance from white paper, or shoot raw and correct from a neutral
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
Neutral mercury has strong visible emission lines at 404.7, 435.8 and 546.1 nm, the last in the green, which appear in fluorescent lamp spectra on top of the phosphor emission.
Source: NIST Handbook of Basic Atomic Spectroscopic Data: strong lines of neutral mercury
FactStrong evidence
Camera white balance is a global linear scaling of the colour channels, so it can neutralise only one illuminant colour at a time.
FactModerate evidence
Auto white balance is ill-posed because the same image can come from a coloured object under neutral light or a neutral object under coloured light, and conventional algorithms struggle in dim or strongly coloured light.
Colourwise interpretationModerate evidence
A green cast confined to skin and shaded surfaces, with whites staying neutral, is more likely reflected light from vegetation than a white-balance error.
Based on: Colourwise reading of the global nature of white balance: a wrong setting shifts neutrals as well, whereas locally reflected light affects only the surfaces it reaches.
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.