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
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