From The Collaborative International Dictionary of English v.0.48 :
Daltonism \Dal"ton*ism\, n.
Inability to perceive or distinguish certain colors, esp.
red; color blindness. It has various forms and degrees. So
called from the chemist Dalton, who had this infirmity.
--Nichol.
[1913 Webster]
From WordNet (r) 3.0 (2006) :
Daltonism
n 1: dichromacy characterized by a lowered sensitivity to green
light resulting in an inability to distinguish green and
purplish-red [syn: deuteranopia, Daltonism, green-
blindness]