More about dichromacy
Dichromacy is red-green colour blindness. It is more common than monochromacy. Mostly men get this type of colour blindness. People with this disorder are missing one of the three cones in their retina. This disorder happens in two types- protanopia, and deuteranopia.
In protanopia, cone cells don't process long wavelengths in red. Reds, oranges, and yellows are dimmed to the point that they may seem black or grey. Pinks, purples, and violets may all appear blue, because the person cannot register the red wavelengths in these colours.
In deuteranopia, cones do not process mid-length waves that are green. Again, reds, oranges, and yellows, and greens all seem the same. Violets, lavenders, purples, and blues also merge into one tone. However, the colours are not abnormally dimmed.
In protanopia, cone cells don't process long wavelengths in red. Reds, oranges, and yellows are dimmed to the point that they may seem black or grey. Pinks, purples, and violets may all appear blue, because the person cannot register the red wavelengths in these colours.
In deuteranopia, cones do not process mid-length waves that are green. Again, reds, oranges, and yellows, and greens all seem the same. Violets, lavenders, purples, and blues also merge into one tone. However, the colours are not abnormally dimmed.