hue that cannot be further described by the use of hue names other than its own
Note 1 to entry: There are four unique hues: red, green, yellow and blue forming two pairs of opponent hues: red and green, yellow and blue.
Note 2 to entry: A "unique hue" is sometimes referred to as an "elementary hue".
Note 3 to entry: This entry was numbered 845-02-36 in IEC 60050-845:1987.
Note 4 to entry: This entry was numbered 17-1373 and 17-1374 in CIE S 017:2011.