@bleedingphoenix @Griffith @Vril_Oreilly @rher @BroDrillard Tyrian purple:
"Purple for dyes fetched its weight in silver at Colophon in Asia Minor. The expense meant that purple-dyed textiles became status symbols, whose use was restricted by sumptuary laws. The most senior Roman magistrates wore a toga praetexta, a white toga edged in Tyrian purple. The even more sumptuous toga picta, solid Tyrian purple with gold thread edging, was worn by generals celebrating a Roman triumph.
By the fourth century AD, sumptuary laws in Rome had been tightened so much that only the Roman emperor was permitted to wear Tyrian purple."

en.wikipedia.org/wiki/Tyrian_purple