Tertiary color if they exist at all, though indigo and scarlet are standard for blue–violet and red–vermilion. In another sense, a tertiary color is obtained by mixing secondary-colored pigments. These three colors are russet (orange–purple), slate (purple–green), and citron (green–orange), with the corresponding three quaternary colors plum (russet–slate), sage (slate–citron), buff (citron–russet) (with olive sometimes used for either slate or citron). Beyond that are shades of grey (blue grey and brown greys), which approach but never quite reach black. The RYB color terminology outlined above and in the color samples shown below is ultimately derived from the 1835 book "Chromatography", an analysis
Color anomaly Color anomaly Colour anomaly, sometimes referred to as partial colour blindness, is an inherited condition in which people have full trichromatic colour vision, but do not make the same colour matches as the majority of the human population. It is much more common than dichromacy or other forms of colour blindness, affecting about 6% of human males in Northern European populations. Two forms are common, known as protanomaly and deuteranomaly. In order to match a given spectral yellow light, protanomalous observers need more red light in a red/green mixture than the majority of observers, and deuteranomalous observers need more green.