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| Cobalt |
| — Colour coordinates — |
| Hex triplet |
#0047AB |
| RGBa |
(r, g, b) |
(0, 71, 171) |
| HSV |
(h, s, v) |
(215°, 100%, 67%) |
| a: Normalized to [0–255] (byte) |
Cobalt is a cool, slightly desaturated blue colour, historically made using cobalt salts. The blue seen on many glassware pieces is cobalt blue and is used widely by artists. It was discovered by Louis-Jacques Thenard in 1802. The world leading manufacturer of cobalt blue in the 19th century was Blaafarveværket in Norway, led by Benjamin Wegner. It is extraordinarily stable. Chemically it is a cobalt(II) oxide-aluminium oxide, or cobalt aluminate. Commercial production began in France in 1807. John Varley suggested it as a good substitution for ultramarine blue for painting skies. "Cobalt Blue" is also a filter used in ophthalmoscopes, and is used to illuminate the cornea of the eye following application of fluoresceine dye which is used to detect corneal ulcers and scratches.
An example of the hue of cobalt blue.
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