Colour Glossary

 

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After-image
Effect of visual stimulation which persists after the stimulus has been removed. After-images are classified according to their appearance compared with the original response: In negative after-images the brightness relationships are reversed. In positive after-images the brightness relationships remain the same. In complementary after-images the hue is shifted to the opposite side of the colour circle.

Achromatic colour (percept)
Colour percept devoid of chromatic content. Note 1 - such colours are the elementary colours white and black and all grey colours which resemble only these. Note2 - achromatic colours are also called "neutral colours".

Chromaticness
The degree of resemblance of a colour percept to the full chromatic colour of the same hue.

Chromatic colour (percept)
Colour percept having a chromatic content. Note - a chromatic colour resembles one or two of the chromatic elementary colours but not simultaneously yellow and blue or red and green.

Colourfulness, chroma
Attribute of a colour percept according to which it appears to be more or less chromatic.

Colour atlas
Collection of colour samples arranged and identified according to a colour order system. Note - often the colour samples themselves or their colorimetric specifications define the colour system. In other systems, such as the NCS, the atlas is merely an illustration of the underlying colour order system.

Colour category
A set of colours which according to a given definition resemble each other.

Colour circle
A circle which illustrates the relationship between all hues.

Colour circle (NCS)
A circle which illustrates the relationship between chromaticness and hue (in the NCS).

Colour contrast
Contradistinction in colour between two colour elements.

Colour difference
Dissimilarity in colour between two colour elements.

Colour interval
The character of a colour difference or colour contrast, analysed with respect to one or more colour attributes.

Colour name
Any verbal expression for a single colour or category of colours.

Colour notation
Description of a colour based on a colour (order) system.

Colour rendering
Expression for the effect of a light source on the colour appearance of objects, judged by conscious or subconscious comparison with their colour appearance under a reference illuminant.

Colour solid
That part of colour space which contains surface colours. Note: - (in some contexts) that part of colour space which can be illustrated with coloured objects.

Colour space
A three-dimensional cognitive model illustrating the relationships between colour percepts.

Colour triangle
Equilateral triangle which, independently of hue, illustrates the relationship (e.g. in the NCS) between whiteness, blackness and chromaticness. Note: - In colorimetry, this term denotes the triangle which in a graphical presentation can be drawn between the three primary stimuli of the system.

Colour vision
The ability to perceive different colours as the result of different colour stimuli.


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Distinctness of border (NCS)
Distinctness of the line perceived as separating two colour elements in contact with each other.

Elementary attribute
The degree of resemblance of a colour to an elementary colour. Note: - the elementary attributes are: whiteness, blackness, yellowness, redness, blueness, greenness.

Elementary colour
Colour percept which can be described only by reference to itself. Note: - there are six elementary colours: white, black, yellow, red, blue and green. The first two are achromatic, the others chromatic. These six colours are also referred to as "psychological colour primaries".


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Hue
Attribute of a chromatic colour percept expressing the degree to which it resembles one or two chromatic elementary colours. Note: - colours with the same relation between the two chromatic elementary attributes are defined as having the same hue (constant hue).


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Lightness
Attribute of a colour element such that it appears lighter or darker than another colour element under the same illumination and viewing conditions.

Lightness value
Numerical value for the lightness of a perceived colour with reference to a scale from black to white.


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Nuance (in general)
Two-dimensional attribute that distinguishes amongst colours of the same hue. Note - Colours of different hues but of the same nuance are also referred to as being "equvalen" or "corresponding".

Nuance (NCS)
Two-dimensional colour attribute which (irrespective of hue) expresses the relationship between whiteness, blackness and chromaticness in a colour percept. Note: - colours of different hues but of the same nuance are also referred to as being "equvalent" or "corresponding".


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Saturation (in general)
The chromaticness/colourfulness of a colour percept judged in proportion to its brightness.

Saturation (NCS)
Attribute of a chromatic colour percept expressing the relationship between its chromaticness and whiteness.