Purple is closely associated with violet. In optics, purple and violet refer to colors that look similar. Purples are mixtures of red light and blue or violet light. Purple is closer to the red hue and violets are closer to blue.
Purple has long been associated with royalty, originally because Phoenician purple dye was extremely expensive in antiquity. Purple was the color worn by Roman magistrates. It became the imperial color worn by the rulers of the Byzantine Empire and the Holy Roman Empire, and later by Roman Catholic bishops. Similarly in Japan, the color is traditionally associated with the emperor and aristocracy.
Purple first appeared in prehistoric art during the Neolithic era. The artists of Pech Merle cave and other Neolithic sites in France used purple dye to draw and paint animals and the outlines of their own hands on the walls of their caves.