The flag is colored orange in Canadian football. NFL penalty flags were colored white until 1965, when the color was changed to yellow. Penalty flags in college football were red until the 1970s. The idea for the penalty flag came from Youngstown State coach Dwight Beede and first used in a game against Oklahoma City 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.