— C o l o u r — unmixed colours

Explanation

Many commentators have proposed the concept of pure, unmixed or basic colours without reference to the mechanisms of human colour vision. These are the psychological primaries or intuitive primaries that would be selected by an ordinary viewer, unschooled in any particular colour theory.

There are now indications that there may be some perceptual basis for the concept. It has even been suggested that the intuitive primaries are connected to opponent colours but there is no neurological evidence for this link.

Intuitive primaries are usually described as black, blue, red, green, yellow and white. In everyday language, each of these colour names has a range of meanings, including those I use in these notes (illustrated below) and what I call green-blue, purple-red, blue-green and orange (illustrated above).

Notes

Most people seem to consider grey to be a mixture of black and white or at least to come between black and white.
Many people consider purple to be a mixture of blue and red or at least to come between blue and red.
I’ve given up asking people what they think brown is. The most frequent answer I got was a shrug. I was taught to make brown by mixing red and green paints, but I don’t think of it as that mixture. I suspect we’re less comfortable dissecting desaturated colours.
There’s no evidence to support Arnheim’s strange claim that green looks like a combination of blue and yellow.¹ I can’t imagine anyone saying that unless they’d been thoroughly schooled in the use of paints. Arnheim uses this statement to justify an unhelpful and otherwise unsubstantiated claim that painters use red, blue and yellow as fundamental primaries, not simply as colours for mixing paint. Even the implication about mixing paints is misleading.

Colour

unmixed colours

Explanation

Notes