When did the color of football penalty flags change from red to yellow?

Question

When I played football in high school in the sixties, the penalty flags were red. Does anyone know in what year the change from red to yellow occurred?

I understand that the red flag now is used for a challenge. But in the 1960's the penalty flags were red. At some point in time, they were changed to yellow and they were changed before the red penalty flags were introduced. I'm trying to determine when the color change occurred.

Answer 1

because red is now the coaches challenge flag :-)

Answer 2

Football Penalty Flag

Answer 3

The yellow flag is for a penalty. The red flag is for the coach to challenge a play.

Answer 4

Television. Red does not show up as well in black and white TV coverage as does the White or Yellow flag.
When the Television went to color coverage, the traditionalists stayed with the brighter colored flag.

Answer 5

Red seems to be a more of a much agressive color, and more important calls, so they gave it to the challenge, yellow is like a normal color and it happens constantly over and over.

Answer 6

when they started nationalizing the stadium fluxes and you couldnt see the colors as well