Intense purple or blue was only worn in the Colonial period.. nobility and royalty.  Synthetic magentas, blues, and purples would not be invented until the middle of the 19th century.  The dye processes and materials to make intense blue or purple cam from semi-precious gems or rare plants that were difficult to transport.

As a result, by the mid 18th century, bright purple had long since been associated with Royals.  Today’s royals still wear purple for State occasions.

(Photo: Queen Elizabeth II wears purple today)