Prussian Blue
Prussian blue has differing chemical names, including iron (III) ferrocyanide, and its chemical formula (which was apparently hard to determine) is Fe7(CN)18(H2O)x where 14 ≤ x ≤ 16.
The Prussian blue of blueprints is the cyanide of the colour cyan, or, cyan is the blue (from the greek) in the name ferrocyanide.
Cyanide is present in almonds and apple seeds.
Not all cyanide compounds are toxic, but many are and are synonymous with poisonings and suicides.
Cyan is not one clear definitive colour.
“The vivid cyan that is seen on an electronic display device is also referred to as electric cyan to distinguish it from the less vivid turquoise-like process cyan used in color printing. (Note: while the color is defined by definite RGB values, the display of the color will vary depending on the absolute color space used and the nature of the physical display device, e.g. computer monitor, and if this page is printed it is likely that the color shown will be far from representative.)”
So, what is cyan, if it’s not necessarily what you see here, not what would be printed, varies from monitor to monitor and “CMYK printing technology cannot accurately reproduce pure cyan as described above (100% blue + 100% green)”?
Is it a Platonic ideal? If you are colour ‘blind’ can you differentiate it?
