Here is another one of those GREEN cars that are not supposed to exist. Again, I have studied this car and am sure it is legitimate. Besides the base color being green the lettering is yellow!
The Pennsylvania hopper came in brown. It is somewhat likely that there is a red version out there but I have never seen one nor have I ever heard tale of one, but, "never say never" with Marx! Green, on the other hand, makes no sense except as a color sample. I cannot imagine a scenario where a brown one is converted to green.
I would like to add a note here to collectors looking for these oddball cars. A color that is non-standard production is a very different animal than a car that shows up in white. A red baggage car could be disassembled, flattened and laid out in the sun. It would not be long before the sun bleached the red out completely and left a white baggage car with black lettering. This could also be affected with chemicals. Not too many years ago, at York, a seller was peddling a scale Fruit Growers Express Reefer that was white with black lettering. His asking price, $1000.00! I examined the car and could detect no sign of tampering but recognized that the yellow could have been bleached out of the litho leaving the black and white "rarity". I passed on the offering! Creating a new color is a very different prospect. If you are interested in collecting these cars I strongly suggest that you take a course in color at your local community college if you are not already trained. A working knowledge of color and the attributes of additive and subtractive color will help you to avoid buying pieces that have been altered. Without giving lessons in faking, I will tell you that many "rare" fakes can be produced with little effort and no money!
This green Pennsylvania hopper is a true Marx color sample.

Here is the undeside of the hopper showing the same typr frame the green Bessemer Boxcar is mounted on.

(Courtesy of Paul Mumford)

This blue PA hopper sold on ebay in 2007. I have not had the opportunity to examine it but I have no doubt it's legitimate.