Any veteran baseball player or spectator is aware of how to utilize the moniker “blue” to get an umpire’s attention. It is reasonable for newbies to the game to inquire as to why umpires are referred to as blue.

Because of the color of the outfit that baseball umpires wear—or, more accurately, used to wear—they are known as “blue.”

The expression comes back to the days when baseball umpires stood on the field in dark navy blue uniforms. When Major League Baseball umpires started wearing light-blue polo shirts in the 1960s, it persisted into the 1970s and beyond.