Tyrian purple

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A reddish-purple dye obtained from certain Mediterranean mollusks of the family Muricidae that was highly prized in antiquity.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A deep purple dyestuff obtained from the bodies of mollusks of the genus Murex
• noun A deep purple colour, tinted with red, like that of the dye.
• adjective Of a deep purple colour, tinted with red, like that of the dye.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a vivid purplish-red color
• noun a red-purple to deep purple dye obtained from snails or made synthetically