Additive and subtractive colour mixing
Beginner
Light adds to white; pigments subtract.
Mixing lights adds (red + green = yellow; all three = white). Mixing pigments subtracts (cyan + magenta + yellow gives dark) as each absorbs colours.
Screens use RGB; printers use CMYK.
Different primaries for each.
In more detail
Additive colour mixing adds light of different colours, with red, green and blue producing white. Subtractive mixing removes wavelengths using pigments, with cyan, magenta and yellow producing black.
Real-world uses
- Screens mix red, green and blue light additively.
- Printers mix inks subtractively using cyan, magenta, yellow and black.
- Screen designers use additive mixing of red, green and blue light, while printers use subtractive mixing of inks.
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Frequently asked questions
Why do paints mix differently from light?
Paints absorb wavelengths, so mixing removes light rather than adding it.
What are the primary colours of light?
Red, green and blue.
Why do paints and light mix differently?
Light adds together when mixed, while pigments absorb light, so each added pigment removes more colours.
Related topics in Optics
Fresnel and Fraunhofer diffraction · Fibre optics numerical aperture · Colour and the eye · Photometry · Geometrical vs wave optics