"The most associated color with Roman Emperor Clothing is the color purple. Only a Roman Emperor was allowed to wear the 'trabea' which was a toga entirely colored in purple and worn on ceremonial occasions. Statues of gods were also dressed in the purple trabea toga, emphasising the importance of the color and of course associating the Emperor with the Roman gods. The purple toga was also referred to as the Toga purpurea. Lesser mortals such as kings, senators, young sons of senators, augurs and some other important priests were allowed to have purple stripes on their togas. The width of the stripe varied accordance to their status." http://www.roman-colosseum.info/roman-clothing/roman-emperor-clothing.htm