Different from the flags used by the officials, what color flag is used by NFL football coaches to challenge the ruling on the field?
Penalty flag University on October 17, 1941. Prior to the use of flags, officials used horns and whistles to signal a penalty. Official adoption of the use of the flag occurred at the 1948 American Football Coaches rules session. The National Football League first used flags on September 17, 1948 when the Green Bay Packers played the Boston Yanks. In some football leagues, coaches are given a challenge flag of similar construction as a penalty flag. The flag is red in American football and yellow in Canadian football, so it contrasts with the officials' penalty flags. This is thrown by a coach
Penalty flag when he wishes to contest (challenge) a referee's decision. Penalty flag The penalty flag (or just "flag") is a yellow cloth used in several field sports including American football and lacrosse by game officials to identify and sometimes mark the location of penalties or infractions that occur during regular play. It is usually wrapped around a weight, such as sand or beans so it can be thrown accurately over greater distances. Many officials previously weighted flags with ball bearings, but the practice was largely discontinued after a flag thrown by NFL referee Jeff Triplette struck Cleveland Browns offensive tackle Orlando