"in the richest inks of Tyrian"

 Tyrian purple is a highly prized ancient dye which comes from sea snails called murex, or Bolinus brandaris. It was first produced by the ancient sea-trading civilisation, the Phonecians ('purple people' in Greek). The dye was so expensive it became reserved by sumptuary laws for use by the emperors of Rome - hence its alternative name, 'imperial purple'.