Don't fool with your monitor. What you see is what it is, a Bessemer Boxcar in GREEN. This demonstrates the caveat "never say never" especially with Marx!
We Marx tin collectors know that the boxcars came in red, blue, brown, yellow and orange, and, when the red is printed over white it creates what has become known as the salmon variation. How then do we explain this green one.

Thanks to Paul Mumford I have now had the opportunity to examine the car. Trip Riley and I examined it together and made the following observations.

The registration is perfect while most production cars are only good.
The deatils are dark green while production cars are black.
The car is on a 1936 or early 1937 era frame (no track clip holes).
It does not appear to have ever been run on track.
The interior is lithographed red (recycled sheet?).
The lettering is silver (actually bright tin plate underneath the green).
No indiaction of tampering or color alteration.

Trip and I have determined that this cars is, without doubt, a legitimate color sample from either 1938 or 1939. This is especially interesting in that is is more proof the solid door boxcar was developed prior to WWII.

(Courtesy of Paul Mumford)