"A person with monochromatism", Late 19th cent.; earliest use found in The Philosophical Review. From German Monochromat from ancient Greek μονο- + χρωματ-, χρῶμα colour.[monochromat etymology, monochromat origin, 英语词源]
"Inability to distinguish between some or (usually) all colours; absence, severe impairment, or loss of colour vision; colour blindness, especially monochromatism", Mid 19th cent.; earliest use found in The Lancet. From German Achromatopsie, †Achromatopsia from ancient Greek ἀχρώματος + Hellenistic Greek -οψία.