Robert S. Butler : Schuweiler's book lists a variation with 2 tone red enamel but he lists this ONLY for the Pullmans and not the Observation. No other explanation. Given that Flyer was in the process of moving to S scale even though they were maintaining O gauge at this time its possible that the color scheme varied even perhaps to using available stock. Who knows?
Thank you for the catalog picture, that helps. I will now try and find the engine / tender...
Don