David, from the photos posted, it looks red for a start rather than maroon.
Decent photos of SLNCR coaches ex-works are red, as few saw a paintbrush in the 50s at all! They weathered to a russet browny red. You might get a reasonable approximation by heavy weathering of that kit.
Eye witnesses described new paint as a shade or two darker than that used by (latterly) GSR, or NCC. That would have been the opinion of jhb171senior, who saw them every day in the 50s. No lining was used, and numerals / lettering was gold or possibly creamy yellow.