Look a little closer
Purple became a royal color largely because one famous version was extraordinarily costly to make. Tyrian purple, prized around the ancient Mediterranean, came not from plant juice but from secretions produced by marine snails.
Making the dye demanded substantial labor. Each snail yielded very little raw material, so producers needed enormous numbers and processed the secretion through several stages. Archaeologists have found great heaps of discarded shells near Phoenician dye-making centers such as Tyre and Sidon.
The result was not one fixed, bright purple. Species, preparation and repeated dyeing could produce shades ranging from reddish purple to deep blue-purple. Makers also used chemical changes that occurred as precursor compounds met air and light.
Rare ingredients and difficult production turned dyed cloth into a visible signal of status. Greek and Roman elites used it in prestigious clothing, and Roman authorities sometimes regulated which ranks could wear particular purple garments.
It is therefore too simple to say that only kings everywhere in the past wore purple. Plant-based purples existed, and customs varied across places and centuries. The exceptional prestige belonged mainly to costly shellfish dye and the political traditions built around it.
Synthetic dyes eventually made purple widely affordable. Yet crowns and luxury packaging still use it because design inherited a long cultural association between this color, scarcity and authority.
