| 1. | a moderate to deep greenish blue. |
| 2. | one of the iron blues, a dark-blue, crystalline, water-insoluble pigment, Fe4[Fe(CN)6]3, produced by reacting ferrocyanic acid or a ferrocyanide with a ferric compound: used in painting, fabric printing, and laundry bluing. |

| iron blue n. Any of various light-resistant and heat-resistant, semitransparent blue pigments of powerful tinctorial strength, used chiefly in permanent industrial finishes, printing inks, and artists' colors. Also called Prussian blue. |
| Prussian blue n.
[From its having been discovered by an 18th-century color-maker in Berlin (then in Prussia).] |
Prussian blue Prus·sian blue (prŭsh'ən)
n.
See Berlin blue.
Prussian blue
any of several deep-blue pigments that are composed of complex iron cyanides and hence called iron blues. The most common of these pigments are Prussian, Chinese, Milori, and toning blue. Prussian blue has a reddish tint and is used almost exclusively in paints, enamels, and lacquers; Chinese blue is very dark, with a greenish tint, and is favoured for use in printing inks; Milori blue has a reddish tint; toning blue is dull, with a strong red tone. All these pigments are chemically similar, differences in shade arising from variations in particle size and details of the manufacturing process.
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