- having two colors.
- (pathology) having a form of colorblindness in which only two of the three primary colors can be distinguished
- (zoology) having two independent channels for conveying color information in the eye.
- (biology) occurring or existing in two different ornamentations or colors, typically as a form of sexual dimorphism.
- (optics) having two hues, either of which may be visible depending on both the concentration of the absorbing substance and the depth or thickness of the medium traversed, such as in pumpkin seed oil. A form of polychromatism.
- (optics) exhibiting dichroism; dichroic.