The color of money
From a very interesting episode of 99% Invisible:
But there are some interesting reasons why the greenback is the way it is. David Wolman, author of The End of Money, explains that the legacy features that make US paper money look stale and anachronistic are meant to convey stability and timelessness. Since the US economy is so important in the world economy, why mess with it? Some fear that changing the design of the currency significantly (or eliminating the penny) could undermine the faith in the federal reserve note.
“Someone once told me that getting rid of the greenback would be like burning the flag on the steps of the Capitol.”