This box shows the colour cobalt blue.
Cobalt blue is a cool blue colour. People used to make it using cobalt salts. Cobalt blue is used widely by artists. Many pieces of glassware have this colour--glassware that does have this colour is called cobalt glass.
The first written use of
cobalt blue as a colour name in English was in 1777. 
John Varley suggested cobalt blue as a good substitution for ultramarine blue for painting skies.
Maxfield Parrish, famous partly for the intensity of his skyscapes, used cobalt blue, and cobalt blue is sometimes called Parrish blue as a result. Cobalt blue was the primary blue pigment used in Chinese
blue and white porcelain for centuries, beginning in the late 8th or early 9th century. 
Tones of cobalt blue colour comparison chart [ change | change source ]
(Dark Powder Blue)
Spanish Cobalt Blue
Cobalt Blue (Gallego & Sanz)
Gallego & Sanz
↑ Maerz and Paul A Dictionary of Color New York:1930 McGraw-Hill Page 91; Color Sample of Cobalt Blue: Page 131 Plate 34 Color Sample L7
↑ " Chinese visual arts » Stylistic and historical development, 1206–1912 » Yüan dynasty (1206–1368) » Ceramics." Encyclopædia Britannica Online. Accessed 14 May 2009.