pigmentation has no recorded synonym. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is depigmentation.
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.
the deposition of pigment in animals or plants or human beings
coloration of living tissues by pigment
Synonyms, antonyms and the broader and narrower relations for pigmentation come from Princeton University’s WordNet. Full sources and licences.