A deficiency of colour vision in which the person can match any given hue by mixing only two other wavelengths of light (as opposed to the three wavelengths needed by people with normal colour vision) - dichromacy, dichromatism, dichromatopsia, dichromia
Type of: color blindness [US], color vision deficiency [US], colour blindness [Brit, Cdn], colour vision deficiency [Brit, Cdn]