metachromatism
/ˌmɛtəˈkrəʊmətɪz(ə)m/noun
1Change of the colour of hair, skin, etc. Now rare.
2 Histology and Biology = metachromasia.
Origin
Late 19th century (in an earlier sense). From meta- + chromatism; in later use in sense 1 probably after French métachromatisme, although in quot. 1876 at sense 1b apparently an independent formation.