WordNet records no synonym and no antonym for tyrian purple. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a red-purple to deep purple dye obtained from snails or made synthetically
a vivid purplish-red color; in ancient Rome and Byzantium, it was the color worn by an emperor or senior magistrate
Synonyms, antonyms and the broader and narrower relations for tyrian purple come from Princeton University’s WordNet. Full sources and licences.