The distinct green tone of U.S. dollar bills wasn't always the norm. In fact, in the colonial era, paper money sported a tan color, accentuated with black or red ink. The notable shift towards the green ink we're familiar with today came about during the Civil War, leading to the term "greenbacks."
The transition wasn't arbitrary; it was a strategic choice to preserve the integrity of the nation's currency. The particular green ink used for printing money was chosen due to its durability and resistance to fading or decomposition. This quality enhanced the longevity of the bills and, importantly, served as a strong deterrent against counterfeiting.