Short answers, pulled from the story.
The earliest known use of yellow ochre in human history occurred approximately 17,300 years ago in the cave of Lascaux in France. This prehistoric pigment derived from clay was one of the first colors available to early artists because it was widely found in nature.
Ancient Egyptians used yellow ochre and the brilliant but toxic pigment orpiment to represent gold, which they believed was the imperishable skin of their gods. In their tomb paintings, men were depicted with brown faces while women and gods were shown with yellow ochre or gold faces, establishing a visual language that linked the color to divinity and eternity.
During the Post-Classical period, yellow became firmly associated with Judas Iscariot, the disciple who betrayed Jesus Christ, and subsequently became a symbol of envy, jealousy, and duplicity. This negative association led to the tradition of marking non-Christian outsiders with yellow, such as the Jews in 16th-century Spain who were compelled to wear a yellow cape before the Spanish Inquisition if they refused to renounce their views.
The 19th century brought a revolution in the availability of yellow through the discovery of synthetic pigments, replacing traditional yellows made from arsenic, cow urine, and other substances. Artists like Vincent van Gogh used commercially manufactured paints like chrome yellow and cadmium yellow, while Georges Seurat used zinc yellow or zinc chromate in his pointillist paintings.
Yellow is the color the human eye sees when it looks at light with a dominant wavelength between 570 and 590 nanometers, placing it between green and red on the spectrum of visible light. Modern optogenetics has utilized yellow lasers at 589 nm and 594 nm, which are less common and more expensive than other colors, to manipulate biological processes.
The Yellow Vests protest in France took place in November and December 2018, where an opposition movement went into the streets to protest against the fiscal policies of President Emmanuel Macron. This event revived yellow as a symbol of political movements in the 20th and 21st centuries after it had been used as a symbol of exclusion during the Middle Ages and Renaissance.