In his early work on light Newton had captured Iris, the mediating rainbow (and anima mediatrix), in a prism of glass and dissected her into seven colors. Iris, the Rainbow Girl, and colors themselves lost their mediating role
Hillman argues that Newton’s prismatic decomposition of light destroyed Iris’s function as anima mediatrix, severing the mediating bond between the phenomenal and invisible worlds that color had carried.
, Alchemical Psychology, 2010thesis