noun
Etymology: translation of French bleu de Prusse
1. usually capitalized P
a. : any of numerous iron blue pigments formerly regarded as ferric ferrocyanide ; especially : one characterized by dark masstones and reddish tints — compare chinese blue 1a, turnbull's blue
b. : a dark blue crystalline salt Fe 4 [Fe(CN) 6 ] 3 . x H 2 O obtained by precipitation from a solution of ferrocyanic acid or a ferrocyanide treated with a ferric salt and used as a test for ferric iron; ferric ferrocyanide
2. often capitalized P : any of the colors produced with Prussian blue, averaging a moderate to strong blue that is greener than orient — called also Berlin blue, bronze blue, Brunswick blue, Chinese blue, Hortense blue, Milori blue, Paris blue, steel blue