What colors no longer exist?

Colors no longer exist can refer to several categories, including pigments that are no longer produced, colors that the human eye can no longer perceive due to rarity, and historical dyes that have been lost. In terms of pigments, some historical pigments no longer exist because their sources are extinct or too toxic or expensive to produce. For example, Tyrian purple, made from thousands of sea snails, is no longer produced commercially in its original form. Mummy brown, made from ground Egyptian mummies, no longer exists for ethical and supply reasons. Lapis lazuli ultramarine was once extremely rare and expensive, but synthetic versions now replace it. Some Crayola crayon colors no longer exist because they were retired, such as maize, raw umber, and dandelion. In terms of perception, there are colors called impossible colors or forbidden colors that the human eye cannot normally perceive, such as reddish green or bluish yellow, which are opponent colors that cancel each other out in normal vision but can be glimpsed in special laboratory conditions. There are also colors that existed in nature but whose sources are extinct, like certain structural colors from extinct birds or insects. So colors no longer exist can mean discontinued commercial colors, lost historical pigments, or colors beyond normal human perception.