Cobalt blue
Cobalt blue in impure forms had long been used in Chinese porcelain, but it was independently discovered as a pure alumina-based pigment by Louis Jacques Thénard in 1802. Commercial production began in France in 1807. The first recorded use of "cobalt blue" as a color name in English was in 1777. The leading world manufacturer of cobalt blue in the 19th century was Benjamin Wegner's Norwegian company Blaafarveværket ("blue colour works" in Dano-Norwegian). Germany was also famous for production, especially the blue colour works ("Blaufarbenwerke") in the Ore Mountains of Saxony.
Cerulean
In classical times, the word "caerulum" was used to describe blue pigments, particularly mixtures of copper and cobaltous oxides, like azurite and smalt. These early attempts to create sky blue colours were often less than satisfactory due to a limited saturation and the tendency to discolour in reaction with other pigments. See also Tekhelet.