A hue circle based on additive complimentary relationships is the relevant choice for all questions where light stimulus is the issue. As there are many kinds of questions where this is relevant, the additive hue circle is particularly important for artists. Some examples include:

  • Results of optical mixing, as in pointillist painting, operate on additive (partitive) principles. Even though we are dealing here with artists paints, we are seeing the result of additive mixing of light from these paints, not subtractive mixing. So, for example, interspersed dots of ultramarine and yellow paint (in the right proportion) will make grey, not the green you would expect from a pigment mixing wheel, and would get if you physically mixed or glazed the same pigments.
  • The coloured afterimage seen after exposing the eye to coloured light for an interval of time is essentially a temporary illusion of light composed of the wavelengths "missing" from the stimulus, and so is the additive complementary. Consequently successive contrast, which is the tendency of these afterimages to influence the apparent colour of other objects, also goes to the additive complementary.
  • Hue shifts due to simultaneous contrast, including the complementary colours seen in the shadows of coloured lights, also go to the additive complementary.
  • Questions of colour harmony, if viewed from the point of view of mutual enhancement of colours, depend on simultaneous and successive contrast, and so should be worked out using the additive hue circle. Ogden Rood (1879) argued that colours within 80 or 90 degrees of each other on such a wheel exhibited negative interactions, and in doing so gave an explanation for the effectiveness of colour harmonies based either on complementary pairs or on equally spaced triads (Figure 7.8).
Figure 7.8. "Chromatic Circle displaced by Contrast, showing the effects produced by red on the other colours" from Rood (1879). The arrangement of colours was determined by experiments with spinning discs, and places colours opposite their additive complements.
  • In colour photography, both conventional and digital, colour correction uses the relationships of the additive hue circle. For example, excessive blueness is countered by adjusting the strength of the additive complementary with a yellow filter.
  • In digital painting programmes, the usual conceptual framework for hue is the Hue angle of HSB and HLS colour space, which is expressed graphically as the RGBCMY hue circle or hexagon (Figure 7.9). This system is based on additive complementary relationships, with the three screen primaries R (scarlet or orange-red), G (yellowish green) and B (deep violet-blue) placed arbitrarily at 120o degrees to each other, and opposite their additive complementaries Y (yellow), M (magenta or red-violet) and C (cyan or blue green).
Figure 7.9. THE RGB-CMY hue circle.

In this system the Hue angle is measured clockwise from "Monitor Red" at 0 degrees. For the fully saturated colours, each 60 degree difference in hue angle between a primary and an adjacent secondary marks a 255 unit change in one of the RGB components (Table 7.1), and so each degree of hue angle represents a change of 255/60 or 4.25 units. The hue angle of desaturated colours is obtained by treating the colour as having a white and a coloured component, and measuring the hue of the coloured component by the same method.

Colour name

RGB components

Hue Angle


R 255



R 255 G 255



G 255



G 255 B 255



B 255



R 255 B255


As always, there is not an exact equivalence between the psychological concept defined by experience and a psychophysical concept defined by the stimulus.  Most observers see tints of H = 0 as more crimson and of H = 240 as more violet than the pure colour, and shades of H = 60 as more greenish and H = 300 as more purplish than the pure colour (Figure 7.10).

Figure 7.10. Variations in perceived hue within colours of identical Hue Angle. Within each horizontal row, all squares have the same "Hue angle", the same R/G/B ratio, and therefore presumably the same dominant wavelength.

In the original conception of the Munsell system (Munsell, 1905), the hue circle was based on additive complementary relationships, in that pairs of opposite colours were chosen that mixed to neutral grey in experiments with spinning discs. Munsell (1905) also regarded his opposite colours, consistently with this, as visual complements. Munsell's thoroughly decimal system specified five principle colours (red [R], yellow [Y], green [G], blue [B], and purple [P]) and five intermediate colours (YR, GY, GB, PB and RP), all equally spaced. Munsell subsequently divided each of these ten principle and intermediate hues into ten clockwise steps, e.g. 5 R is the hue in the middle of the range of the principle hue red.

Adjustments based on extensive colourimetric measurements in the 1940's resulted in what is known as the renotated Munsell System, which is widely used today as a means of specifying colour in science and industry, as well as among a relatively small but committed band of painters. The renotated system allows conversion between Munsell and CIE specifications (such as L*ab), and thereby to approximate RGB values (or precise values if the particular RGB space is specified). The three pairs of screen primaries and secondaries red-cyan, green-magenta, and yellow- blue, which are exact additive complements in any specified RGB space, return Munsell hues that are roughly opposite in the renotated system, though not exactly so in the case of yellow and blue (Figure 7.11). In addition, the angular spacings between the three pairs in the Munsell system differ noticeably from those of the RGB-CMY hue circle, but not in a way that has an obvious superiority in perceptually equal spacing. These differences between the two hue circles are of relatively small practical importance, however; both the RGB-CMY and the Munsell hue circles make suitable conceptual frameworks for artists in situations when additive complementary relationships are relevant.

Figure 7.11. Munsell hue circle, with indicative positions of the RGB primaries and secondaries shown by coloured dots. The Munsell hues were obtained using Wallkillcolor's Munsell Conversion Software for the colours at 80% brightness (to avoid artefacts that arise in the conversion of some RGB colours with values near 255), assuming illuminant C, 2o observer. The actual values returned were: Red (R 204) = 8.03R; Yellow (R 204 G 204) = 0.56GY; Green (G 204) = 9.71GY; Cyan (G 204 B204) = 8.05BG; Blue (B 204) = 6.68PB; Magenta (R 204 B 204) = 8.19 P.

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