Ford factory trivia
All of this talk regarding the underside colors of a Mustang got me to thinking about what I have learned about Cougars.
Cougars had sound deadener installed from the factory which included a light coat of undercoating to the bottom of the car. The bottoms of Cougars were painted slop grey. Slop grey is a mixture of paints that were poured into a common container and used for the undersides of Cougars at the Dearborn plant, most likely the San Jose plant too. The thought was that the color of the undercoating wouldn't contrast like the red oxide color might. Plus it was a way of paint recycling at the end of the day/shift.