"Prussian blue was the first modern synthetic pigment. It is prepared as a very fine colloidal dispersion, because the compound is not soluble in water. It contains variable amounts of other ions and its appearance depends sensitively on the size of the colloidal particles. The pigment is used in paints, and it is the traditional "blue" in blueprints and aizuri-e (藍摺り絵) Japanese woodblock prints.

In medicine, orally administered Prussian blue is used as an antidote for certain kinds of heavy metal poisoning, e.g., by thallium(I) and radioactive isotopes of caesium. The therapy exploits the compound's ion-exchange properties and high affinity for certain "soft" metal cations.

It is on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system. Prussian blue lent its name to prussic acid (hydrogen cyanide) derived from it. In German, hydrogen cyanide is called Blausäure ("blue acid"). French chemist Joseph Louis Gay-Lussac gave cyanide its name, from the Ancient Greek word κύανος (kyanos, "blue"), because of the color of Prussian blue."
"In the Byzantine Empire, the Blues and the Greens were the most prominent political factions in the capital."
"FIFA World Cup winners Italy, who wear a blue kit based on the Azzuro Savoia (Savoy blue) of the royal House of Savoy which unified the Italian states, despite the italian national flag being green, white and red."