Not to throw the proverbial t... in the punch bowl, but why red when there's overwhelming evidence that at least the Firestone belts were brown? As I am sure most of you know, in 1932 Ford changed all of the part numbers of A parts carried over into the B engine with a B part number prefix. So, A-8620 became B-8620 in the late version of the 1932 chassis parts catalog and all those that followed. Same belt, same function, and a new part number prefix.
Having been in the hobby since the 1950s, I've had the good fortune to be able acquire parts that have long since become extremely scarce, with fan belts being a good example. So far, nearly all of my '32 four and V8 restorations are equipped with Firestone fan belts with molded-in part numbers and the unique Firestone trademark "F" and all of them are brown, not red. (There were red fan belts in the period, but seemingly not those made by Firestone.)
While color photos in Ford's archives before 1939 are rare, one exception of a 1932 V8 display chassis is further evidence of the fan belts (at least those produced by Firestone) being brown in color.
I claim no expertise when it comes to Model As, but common sense suggests it unlikely that the color of the Firestone fan belts was changed at Job#1 for the 1932 models.