In Iridology, there are only three eyes colours. Blue, Brown, and Mixed/Biliary. Although many claim to have colours like hazel or green, information in Iridology is drawn from these three colours. Each colour has genetic traits that dictate a set of potential predispositions.
Everyone has blue eyes under their unque colour. The pigment that lays brown on the eyes is covering the natural blue undernieth. The blue eyed person, however, has a tendency towards lymphatic/immune system pathology, kidney conditions, acidity, inflammation, and rheumatism.
Brown eyes people have more of a tendoncy towards blood/circulatory illness. The traditional name, "hematogenic", is in reference to heme or blood metabolism and iron. Also this person has more of a tendency towards digestive system problems, especially of the liver.
Biliary/mixed eyes are more like brown eyed people but with more of an emphasis on liver/gallbladder. These three colours are used to assess the basic genetic traits associated with each type. In addition to the colours found genetically, we can also pick up colours via internal toxicity. In this way, an Iridologist can find organic/metabolic diharmony prior to an illness forming. For example, inflammation forms in the eyes as a whitish, raised look. This would be seen as an addition to the normal colour of the eye. Wherever this whitish look appears, that organ, according to the chart of Iridology, is affected.