[mreid]

From an archive perspective, CSX2557 and CSX2558 were both delivered unpainted with black trim (designated for racing). CSX3002 through CSX3101 were also delivered unpainted (several were chassis only). As was CSX3127 and CSX3139. CSX3170 is an AC car and was delivered silver with black trim.

This doesn't answer your original question as the unpainted ones were for the most part later painted with race team colors. Other than hearing from a current owner, I don't know how we would ever know if any orignal ones are today unpainted.