The exterior of the finished passenger car model is based on the original color scheme as delivered by the Cincinnati Car Company in 1909: Pullman Green body, Tuscan Red roof, Mandarin Red doors and sashes, gold lettering and stripes.
At some point the railway’s cars were repainted completely in red, but I haven’t been able to determine when that happened. But even if I learned that it happened before 1916, I’d be tempted to leave the original colors. They look pretty sharp.
A little rust on the trucks and undercarriage and a moderate amount of chipped paint and dust on the body has been added to show that the car has been in use for few years.
The model fits perfectly on the existing railway tracks in the Terragen scene. The image below shows the approximate final angle and framing of the scene with the car in place.