Goethe's hue system

Given that the four psychological primaries are the basic building blocks of our experience of hue, it is not surprising that they turn up repeatedly in colour order systems long before their explicit recognition by Hering and his contemporaries. In the middle ages Theodoric of Freiberg saw these four hues as the colours of the rainbow (Kuehni and Schwarz, 2008, p. 36), and the same four appear alongside white and black as the simple colours in the systems of Leonardo (Fig. 7.1.2D) and Forsius (Fig. 7.1.3E) (section 7.1). (They have also been seen by some in the system of Alberti, though it seems more likely that his four simple colours were intended to be red, green, blue and grey). Credit for a major step towards the concept of opponency must go to Goethe, whose theory of the origin of colours is based on an explicitly opponent relationship of the yellow and blue primaries (Fig. 7.3.2A). For a very concise summary of the essence of this theory please see this paragraph.

Hooke and Huygens had previously suggested that yellow and blue were the two fundamental primary colours, but Goethe also came close to recognizing red and green as pure or simple colours, despite believing the latter to be a mixture of yellow and blue, and his theory indirectly contrasts pure red (his purpur), seen as the result of "augmentation" or reddening of both blue and yellow, with middle green, seen in his theory as a balanced, simple mixture of the two (Fig. 7.3.2B).

Figure 7.3.2. Quotes from Goethe's writings concerning yellow, blue, red and green.

One might say that despite his theory of the origin of colour, which itself has no physical or psychological validity, our innate opponent framework of colour perception made its presence felt in Goethe's choice of hue terms to describe that theory. This opponent framework emerged most openly in his section on colour terminology, where he proposed a fully opponent system of 12 hue names formed as combinations of the four symmetrically arranged hues red, yellow, green and blue, in which no hue names are combinations of yellow and blue, or red and green (Fig. 7.3.3A, B). Goethe himself pointed out that this four-hue system is suggested by the German language itself.

Figure 7.3.3. Goethe's 12-step opponent system of hue terminology (B) and its relationship to his three afterimage "complemental " pairs (C), indicated with red arrows in both.

Goethe's unique foreshadowing of opponency is sometimes confused with his discussion of afterimage complementary ("complemental") colours, which were already known in the eighteenth century. Goethe himself must have recognized that two different kinds of opposite relationship were involved, as two of his complemental pairs diverge from his primordial opposition of yellow vs blue (Fig. 7.3.3B,C). [In Goethe's theory these oppositions would be considered subjective and objective respectively]. The third complemental pair, recorded as "purpur"-green, on the other hand was made to align with the red-green axis by using the term "purpur" with two distinct meanings. Unique red and unique green are not additive or afterimage complements - the complement of middle green is magenta and vice versa. "Purpur" literally means "purple", and is the name Goethe used for the magenta afterimage-complement of "balanced" green, and also for a magenta colour appearing in edge spectra that, in modern terms, is the additive complement of spectral green (Fig. 7.3.4). However "purpur" also has an important place in Goethe's theory as the ultimate degree of the "augmentation" or reddening of both blue-red and yellow-red, and in this role is necessarily as well as explicitly described as an absolutely pure red, neither yellowish nor bluish (Figure 7.3.2B). Consistently with the latter, it is also described as being the colour of fine carmine, intermediate between the slightly bluish and slightly yellowish varieties of the colourant (Goethe, Theory of Colours, 796, 799-800). Goethe used "purpur" as a "weasel word" that could be defined as pure red (about Munsell 5R), but could be stretched where needed to include the distinctly bluish (magenta) afterimage and additive complements of green (roughly Munsell 10P to 5RP).

Figure 7.3.4. A. Goethe's illustrations of the edge spectra seen when a white band on a black background (left) and a black band on a white background (right) are observed through a glass prism from various distances (Theory of Colours, 243-6, pl. 2). In Goethe's view the green in the middle of the lower two light spectra is formed by mixing of the yellow and blue fringes seen separately in the upper view (see explanation to Fig. 6.2.6). The magenta colour labelled "purpur" in the middle of the corresponding 'dark spectra' is in modern terms the additive complement of this green. B. Simulation of Goethe's experiment.

Hering and Ostwald

Figure 7.3.5. A, Hue circle and B, diagrammatic hue page showing a colour specified in terms of black (b), white (w) and full colour (r) components (Hering, Outline of a Theory of Light Sense, tr. Hurvich and Jameson, 1964). C. Hering's six fundamental colours arranged in a distorted octahedron, from Ebbinghaus' Psychology, an elementary text-book (1908), translated from his German text of 1897.

In the original opponent theory of Ewald Hering, white and black, together with red, yellow, green and blue, were regarded as the six fundamental colours of visual perception. In Hering's view, all colours could be considered as mixtures of full colour (pure hue), white and black components (Fig. 7.3.5B). This was a major departure from most other systems, which instead used relative or absolute lightness or brightness as an important dimension. Hering did not attempt to provide colour samples arranged according to his system, apart from his purely illustrative hue circle (Fig. 7.3.5A, Fig. 6.2.9).

As Hering himself noted, several other 19th century psychologists had already settled on red, yellow, green and blue as the four fundamental hues, and the four-hue system began to appear frequently in psychology texts from around the turn of the century, including those of both Hofler and Ebbinghaus in 1897 (Fig. 7.3.5C) and Titchener in 1901 (Kuehni and Schwarz, 2008, pp. 101-3). Nevertheless, Hering's theory was still often presented as a less likely alternative to the trichromatic theory of Helmholtz and others until the idea that the two could be combined in some form of zone theory eventually gained general acceptance, particularly through the efforts of Leo Hurvich and Dorothea Jameson in the 1950's. The four psychological primaries are now explicitly acknowledged in the official definition of the word "hue" by the Commission Internationale de L'Eclairage (CIE) as "the attribute of a visual sensation according to which an area appears to be similar to one of the perceived colours, red, yellow, green and blue, or a combination of two of them".

Figure 7.3.6. Ostwald system. A, Ostwald's four principal and four intermediate hues from his Die Farbenfibel (1917) . B, Analysis of a colour into white (d), black (e) and full colour (f) components, from his Einfuhrung in die Farbenlehre Vol 2 (1919). C, model of the Ostwald system showing double-cone form (wikipedia). D, Blue/yellow and seagreen/red hue pages from Ostwald's colour atlas, Der Farbkorper (1919).

Wilhelm Ostwald (1853-1932) published the first atlas of colour samples influenced by Hering's opponent theory. Ostwald followed Hering in classifying colour in terms of white/black/full-colour content, and structured his hue circle around four principal hues, but in order to make opposing colours additive complements, the place of the green psychological primary was taken by a bluish green known as "sea green". The Ostwald system was widely used in art education in the middle decades of the twentieth century, was the official system for all levels of art education in Great Britain between the wars (Fig. 7.3.7A), and was promoted worldwide in many popular books on colour for artists by authors such as Faber Birren. The system was gradually abandoned in the scientific community beginning in the 1940's, and by the time the quasi-opponent CIE L*a*b* and CIE L*u*v* systems were developed in the 1970's, the tide had turned strongly against the inclusion of techincal elements in general in art education. In recent decades the three primaries of "traditional" colour theory have become so prevalent in the education systems of most countries that many artists today assume that they have been used universally for centuries.

Figure 7.3.7. A. Colour plate from Colour Practice in Schools by O.J. Tonks, Winsor and Newton, London, 1934. B. An Ostwald watercolour box, by Winsor and Newton, c. 1930's. C. The Color Harmony Manual, a spectacular colour atlas based on the Ostwald system, sold by the Container Corporation of America from 1946 to 1972.

The NCS system

Figure 7.3.8. A. Opponent-hue circle from Johansson's Den allmanna farglarans grunder (1937). B, Hue circle from Hesselgren's Fargatlas (1953), structured around the psychological primaries, but also expressing perceptual hue spacing by placing varying numbers of hues in the four quadrants.

A different Hering-inspired approach was suggested in 1937 by the Swedish physicist Tryggve Johansson (1905-1960). Johansson designed an opponent hue circle (Fig. 7.3.8A) that could be used in three alternative systems in combination with dimensions of (1) chroma and lightness, (2) saturation and lightness, and (3) chroma and "cleanness" (a converse of black content). The Swedish architect Sven Hesselgren (1907-1993) produced an atlas of colour samples using the second of these proposals, but although Hesselgren's hue circle was likewise structured around purely opponent hue axes, it also expressed perceptually-equal spacing by placing varying numbers of hue divisions in the four quadrants (Fig. 7.3.8B). Later both Johansson and Heselgren contributed to the development of the Swedish NCS system, in which both the hue circle and the hue pages are structured in line with Hering's system (Kuehni and Schwarz, 2008).