Y: We use money all the time Don, but have you ever wondered why U.S. banknotes are green.
D: I’d guess that the Treasury Department must get green ink at a discount, Yaël.
Y: Well, I did some investigating into the history of the Bureau of Engraving and Printing, and it turns out that there are several reasons for the green-back design.
D: Tell me more.
Y: The Treasury introduced small-sized notes in 1929, and it used green pigment because it was cheaply available in large quantities. Green retained a high resistance to chemical and physical changes, and there was scientific evidence that consumers psychologically identified green with the strong and stable credit of the government.
D: What about prior to 1929?
Y: The Bureau of Engraving and Printing had gradually taken over full responsibility of printing banknotes since the end of the Civil War. During that time, the government had sole access to the iconic “patent green” ink. This protective ink did not fade or decompose easily. That protected against counterfeiting.
D: So, did banknotes ever come in colors other than green?
Y: During the American Revolution, the Continental Congress printed tan dollars, embossed with black ink. These were square bills made of a cloth mixture of silk and sometimes isinglass, which is a thin, opaque substance, made from fish air bladders. The unique composition of the bills was supposed to prevent counterfeiting.
D: And of course, the modern-day ten-dollar bill is mostly yellow and orange...Y: …Yet another innovation to curb counterfeiting. The website for the Bureau of Engraving and Printing says that most U.S. banknotes are still green because it simply has no reason to change them.