What word or phrase does your mother always say?
dichromatism di·chro·ma·tism (dī-krō'mə-tĭz'əm)
The state of being dichromatic.
A form of colorblindness in which only two of the three fundamental colors can be distinguished due to a lack of one of the retinal cone pigments. Also called dichromatopsia, dyschromatopsia, parachromatopsia.