Up until the late 1970's Soo painted their gondolas brown with white lettering (they did have a few covered gondolas in the late 1960's painted in the Colormark scheme withe black lettering but they didn't last long)
In 1977 Soo Changed their Paint Scheme. on locomotives the went from the curved red on the cab to the "Hokey Stick" (which was used on the parallelogram scheme). They also changed the black lettering to Red.
The first order of Soo GP38-2's were delivered in red, a handful of boxcars were repainted and most significantly there were three major orders for Gondolas (both 50' & 65' bulkhead)
The Red Lettering was short lived, It was dropped by 1978 and Soo's next order for gondolas was back to brown.
As for Black lettering the closest thing I could find was this photo of a gondola with Hopper style green lettering, now considering it was one of the cars ordered in 1977/1978 it was probably delivered in red...
http://www.rrpicturearchives.net/showPicture.aspx?id=337838
