Dichromats have two cone photopigments instead of three and are able to match all spectral hues using a mixture of just two colors. They are further classified as protanope (long-wavelength pigment missing), deuteranope (medium-wavelength pigment missing) and tritanope (short-wavelength pigment missing).
The prevalence of the various forms of dichromacy are as follows:
| Type | Men % | Women % |
| Protanopia | 1.0 | 0.02 |
| Deuteranopia | 1.1 | 0.01 |
| Tritanopia | 0.001 | 0.001 |
Dichromats are able to discriminate on the basis of wavelength alone, although their sensitivity is reduced compared to normal trichromats. Therefore affected individuals can be described as color deficient, not color blind.