The color purple refers to Tyrian purple, restricted by law, custom and the expense of creating it to royalty.
The shell is thought to be a murex shell; this was the source of Tyrian purple (in Latin: purpureo) and this, along with the letters, is thought to refer to a Furius Purpureo.
Deep Purple | Purple Heart | The Color Purple | Purple Rain | The Color Purple (film) | Purple Hairstreak | Purple-rumped Sunbird | Purple Rain (film) | Purple Gang | Tyrian purple | Purple Rain (album) | Purple people | Niagara Purple Eagles women's ice hockey | New Riders of the Purple Sage | The Purple Plain | The Purple Jar | The Purple Gang | Purple-tailed Imperial Pigeon | Purple-crowned Fairywren | purple | Niagara Purple Eagles | The Purple Rose of Cairo (fictional film) | The Purple Rose of Cairo | The Purple Prince of Oz | Purple Rain (song) | Purple People Eaters | Purple (magazine) | purple loosestrife(''Lythrum salicaria'') | Purple | Military Order of the Purple Heart |
On the right is a mosaic depicting the East Roman Emperor Justinian I, clad in Tyrian purple with a golden halo, standing next to court officials, Bishop Maximian, palatinae guards and deacons.
There have been studies on some species within the family Muricidae, because in those species this gland secretes the precursor to the historically important natural dye, Tyrian purple.