NS Bethgons

I thought it would be an easy find. Somehow the new search engines come back with every other thing than what I asked for?

Well, at least it is not me.  It seems that search engines have become uber focused on models that can be sold rather than prototypes.

You'll notice the model is in Athearn's "Primed for Grime" series, which attempts to replicate rolling stock that has been in service a while by pre-fading paint, and the addition of patchwork paint repairs and such depending on the prototype. From the page:

"PRIMED FOR GRIME MODELS FEATURE:

• Duplicated look and feel of “In Service” equipment; “Tattered and Torn” just like the real thing
• Faded base colors matched to the prototype
• Patches applied and shaped per road number matching each corresponding side to the prototype
• Perfect starting point for adding grime and rust"
  
  
  I found pictures of these cars right off the bat on Railcarphotos and Fallenflags. It looks like the Athearn artwork is depicting where the prototype cars had different materials making up the car sides (steel vs aluminium??). It looks pretty exaggerated on the artwork, but I can see looking at photos of the real cars where the shiny aluminum sides could create a color cast, based on the light they are reflecting. But none look especially blue as the artwork.
  
  Having said that, Athearn's artwork is not always error-free... infact, that can be a contentious issue with the more serious prototype modelers, but that's a different story. For what it's worth, the HO scale version of the car doesn't have the "blue" ends, and MTH's O gauge version of this car also lacks them (but does capture the mixed-material construction).

Excellent point.  So what you are saying is it really is more like this

Because of different material used in the ends than the sides.  I think you are correct.  Thanks!