Colorblindness, red-green: A form of colorblindness in which red and green are perceived as identical. This is the most common type of colorblindness. It is also known as deuteranomaly, deuteranopia, and Daltonism.

The term "Daltonism" is derived from the name of the chemist and physicist, John Dalton (1766-1844). Dalton was born in a village in Cumberland, England where his father, Joseph, was a weaver in poor circumstances. He was educated by his father and John Fletcher, teacher in a Quaker school. When Fletcher retired in 1778, Dalton took his place. In 1793 he was appointed teacher of mathematics and natural philosophy at New College in Manchester. In 1803 he put forth the facts embodied in his law of partial pressures: the pressure of a mixture of gases is the sum of the pressures which would be exerted separately by the several constituents if each alone were present. Dalton's reputation largely rests upon his great Atomic Theory. It was said of Dalton that "into society he rarely went, and his only amusement was a game of bowls on Thursday afternoons."

Dalton described his and his brother's affliction of colorblindness with defective perception of red and green in the first scientific paper he published. It was entitled "Extraordinary facts relating to the vision of colours, with observation" (Mem Literary Philos Soc Manchester 5: 28-45, 1798). It is the first recognized account of red-green colorblindness.