Explain the Dichromates or Mild Colour Blindness

A dichromate individual possesses only two cone pigments. Lack of the red pigment, called protanopia, makes distinguishing of the red and green colours impossible and the visual system is insensitive to deep red colours. Similarly, the lack of the green pigment, called deuteranopia also makes the differentiation of red and green colours impossible but the visual system is nevertheless sensitive to light in the range normally served by green pigment because responsiveness of red and blue pigments overlaps into this range. Dalton was red green blind. Just imagine him driving a car at a traffic light signal! Lack of the blue pigment, called tritanopes makes the discrimination of blue and green colours impossible.