When we envision what a ninja looks like, it’s typically a person dressed all in black, carrying a sword, and throwing stars. But that’s not exactly true. While they did carry these types of weapons, ninjas did not wear black.

It turns out that the most effective color for a ninja to wear is actually navy blue because at night, black clothing will stand out more than blue. If you would like to see it for yourself, check with the Ninja Museum in Igaryu, Japan. On International Ninja Day, celebrate the history of these silent warriors and hope that we don’t end up on their bad side. Because if you do, you’ll never see them coming.

Today we also celebrate: National Sacher Torte Day, National Repeal Day, and Bathtub Party Day.