dichromat

It can be used to determine whether a person is a tritanope, dichromat or achromatop.

The goal of the gene therapy is to make some of the cones in the retina of a dichromat individual to express the missing photopigment.

Mancuso et al. published their research in the journal: Nature in 2009, on converting adult dichromat squirrel monkeys into trichromats using gene therapy.

The cones excited to a corresponding colour in the colour space are visible to the dichromat and those that are not excited are the missing colours.

A certain pair of colors, that seem very different to a normal viewer, appear to be the same color (or different shades of same color) for a such dichromat.

Exponentiation suggests that a dichromat (such as a human with red-green color blindness) would be able to distinguish about 10,000 different colours, but no such calculation has been verified by psychophysical testing.

The description of the phenomena itself does not indicate the colour that is impaired to the dichromat, however, it does provides enough information to identity the fundamental colour space, the colours that are seen by the dichromat.