All languages contain terms for white and black. If a language contains three terms, then it contains a term for red. If a language contains four terms, then it contains a term for either green or yellow (but not both). If a language contains five terms, then it contains terms for both green and yellow. If a language contains six terms, then it contains a term for blue. If a language contains seven terms, then it contains a term for brown. If a language contains eight or more terms, then it contains a term for purple, pink, orange, gray, or some combination of these.
– Berlin & Kay, Basic Color Terms: Their Universality and Evolution, 1969
– Illust: Antique color wheel; Color Chart, Gerhard Richter