Classifications of Colour

Chromatic

Colours

Chromatic colours include any colour that is predominantly: red, orange, yellow, green, blue, violet, or a combination of these.

Mixtures

Mixtures include all colours that combine different wavelengths.

This includes almost all grayscale colours, as grayscale colours are the combination of an equal amount of all wavelengths of light. This excludes white, in the case of pigments, and black, in the case of light. Most mixtures are chromatic, as they have a hue. All mixtures are either chromatic or non-spectral.

Grayscale/ Achromatic colours

Grayscale colours include black, white, and all shades of gray.

All grayscale colours are non-spectral. No grayscale colours are chromatic, as the have no predominant hue. In the case of pigments, white is not a mixture. In the case of light, black is not a mixture.

Spectral/ Mono-chromatic colours

Spectral (aka monochromatic colours) are made up of one wavelength of light.

Non-spectral

colours

Non-spectral colours include grayscale colours, colours which are mixtures including grayscale colours, impossible colours, and metallic colours.

Colours which are chromatic, non-spectral, but not a mixture may include some metallic colours. Colours that are chromatic must either be spectral (aka monochromatic) or mixtures, depending on how many wavelengths are present.

Non-spectral colours which are mixtures, but are not grayscale, may include some metallics.