Where I live, all money is green and visually impaired people learn to tell a dollar bill from a hundred by feeling the paper; in most of the rest of the world, however, currency colors vary depending on denomination. In some countries the size of the bill/note is related to the value but not always. Knowing the main color of a bill could be helpful in identifying its value. Here is an affordable innovation from a young Brazilian engineer that attempts to solve this problem
http://www.auire.com/2010/01/the-solution/
Last updated: December 26th, 2025
