By Dr. Robert Hirschler, Chair, AIC Study Group on Colour Education.

Artists, architects and designers should learn the basics of colour science, but do they? The dozens of books on colour aimed at this audience are full of misconceptions and gross errors. This presentation will summarize some of the basic concepts which are considered useful knowledge even for non-scientist.

One of the sources of the worst misconceptions is the treatment of “light-colour” vs. “pigment-colour”. An otherwise excellent text-book starts with the statement, that “Newton’s work became the dominant school of thought on additive colour”. But Newton’s work is equally valid for object colours, and we shall see how the light, reflected by coloured objects, is composed of a combination of monochromatic lights (i.e. of rays of different wavelengths) and thus every colour we see may be considered an “additive mixture” of monochromatic lights. By the same logic what is generally considered to be “subtractive colour mixing” is not, in fact, the mixing of “colours” but that of colorants. We can demonstrate the rules of “subtractive mixing” by projecting a mixture of coloured lights and blocking one or more components. In order to understand the behaviour of coloured light (and thereby the behaviour of dye or pigment mixtures) some knowledge of spectral curves may be useful.

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Another constant source of problems is the discussion on colour wheels (hue circles). Colour wheels are useful in illustrating colour relations, but there are not one but many colour wheels, very different in concept and you must make sure to define which colour wheel you mean before embarking on a discussion of colour mixing or colour harmonies. Here we shall discuss the fundamental problem of the RYB (Itten) colour wheel and why it is all wrong. Colour is three dimensional, so colour wheels are only a part of the story, there are different ways of specifying colours in 3D, and we shall discuss briefly the possibilities of using the Munsell, NCS, CIELAB, HSV and HSL systems.

Artists and designers should be particularly aware of the relativity of colour (in the sense of Albers’s Interactions). Yet in many textbooks we find statements to the effect that wavelength = hue. This is very wrong, we can find an infinite number of wavelength compositions resulting in the same colour stimulus (these are called metameric colours), and also, we may produce very different colour sensations (perceptual colours) from the same spectral compositions, as strikingly illustrated by the phenomenon of coloured shadows.

All through the presentation we shall discuss many of the common misconceptions – so that they can be avoided.