What's the noun for purple? Here's the word you're looking for.
purple
A colour/color that is a dark blend of red and blue; dark magenta.
Cloth, or a garment, dyed a purple colour; especially, a purple robe, worn as an emblem of rank or authority; specifically, the purple robe or mantle worn by Ancient Roman emperors as the emblem of imperial dignity.
(by extension) Imperial power, because the colour purple was worn by emperors and kings.