Purple is a color between blue and red
Purple was a sign of nobility due to the high costs of Tyrian purple, a dye first produced by Phoenicians or even before in Crete (around 20 century B.C.). According to the legend, it was discovered by Heracles' dog, who ate some snails found in the eastern Mediterranean Sea.
Phoenicians established a colony on a group of islands in front of Morocco called today Îles Purpuraires, off to Mogador, where the sky looks sometimes purple as well.
But thousands of snails were required to dye a single cloth, so the "purpura" was very expensive, a luxury reserved to the nobles. The Roman Emperors used to wore a purple clad. The idiom "Born in the purple" meant "born among the nobles".
The process lasted centuries, till Constantinople fall to the Muslims. Short after that, Europe learned about cochinilla, an insect who grows on nopales used by Mayas and Aztecs to dye red. French called it vermillon.
There is even a rare and gorgeous purple marble used in Italian churches, like this columns in a Roman church.
More recently, Jimmy Hendrix popularized among the hippies the psychedelic purple with his movie and song "Purple Rain".
When I think of purple I have to think of Rufino Tamayo and his love for this color. Here, just a single example: "Retrato de niños - Pareja de niños" (1966).
Photographs of the 80s and made with a Polaroid camera used to obtain a particular violet-like tone, like this beautiful shot by Anna Beard of Bello Ucello.
But the real Purple Rain occurred rather in Cape Town, when the police decided to use purple water against the anti-apartheid demonstrators in 1989.
I. Mojica, "Jacarandas en primavera" (2008)