Purple - the colour of high status.

Purple (corcur in Irish) the royal or imperial colour. The ancient Irish were acquainted with the art of dyeing purple using a rock lichen and shellfish like cockles. Heaps of shells have been found, all broken uniformly at one particular tip, inside which was situated an elongated little sac containing the purple colouring matter. Evidently the shells were broken in such a manner that the object was the extraction of a precious little globule.

The purple dyestuff, however obtained, was produced in very small quantities, so that it was extremely scarce; and the colour was excessively expensive in Ireland as elsewhere: on the Continent in old times it was worth thirty or forty times its weight in gold. Partly for this reason, and partly for its beauty, purple was a favourite with kings and great chiefs, so that writers often designate it a royal or imperial colour.

Image: Book of Kells Folio 32v shows Christ enthroned. Note the purple garment indicating high status.