John Dalton was a tornado of English science, exploring atomic theory, meteorology, perception, and the physics of gases with equal avidity.

But he was a Quaker, and when in 1834 he was invited to be presented to William IV, the question arose whether he could properly appear in the scarlet robes of an Oxford doctor of laws, as the color was forbidden to him.

Dalton solved this neatly: He pointed out that he was color-blind. “You call it scarlet,” he said. “To me its color is that of nature — the color of green leaves.”