
Maybe yellow , gray ? What color are their flat cars , anybody know ? Guesses ?
This appears to be a builders photo with the car painted in grey and black (note the grey coupler - and the trucks appear to be a lighter color, you can make out the truck springs which would be impossible if the trucks were black). This gray with black was fairly common practice in the 40's and 50's for several RR's for the first car of a series.
I am betting that the in service scheme was yellow with black lettering because of the novelty of the auto rack concept at the time (aren't the auto's 1958's?) and as was pointed out the Frisco went with yellow and black for the tri-levels a few years later. I think the auto-racks were the first Frisco yellow cars but yellow became the Frisco color for Cushioned cars and other speciality cars - But, it was never a fleet color, the standard boxcar color always remained brown.