You Say Blue, I Say Cerulean

Color Dictionaries Gave the World a Common Language—and Names Like ‘Dragons-Blood Red’ and ‘Light Paris Green’

Attached to an actuator on the shoulder of NASA’s Curiosity Rover exploring Mars right now is a set of panels that looks like an eye shadow compact. It has six pigmented silicone panels—in red, green, blue, 40-percent gray, 60-percent gray, and one in a fluorescent pigment that glows red under ultraviolet light. This is the color calibration target for Curiosity’s Mars Hand Lens Imager, a camera that takes landscape portraits and close-up shots of rocks on Mars (and also selfies). Geologists want some way to know what color these Martian …