No tank engines carried snails, and all cie narrow gauge engines were tank engines.
Until about 1949 onwards, locos continued the GSR practice of cast numberplates painted over grey like the rest of the loco. Sometimes the numerals were picked out in cream or pale yellow, sometimes not at all. All narrow gauge locos under the GSR and CIE were all over grey, chimney, smokebox, cab, motion and wheels included. None got the black which a few 5ft 3 locos got very late in the day.
So, it's plain grey for everything!
After 1949, many locos had their numberplates removed and large painted pale yellow numerals placed on tank sides instead.
Buffer beams were technically red, but many were in practice so weathered, faded and dirty that they were indistinguishable from the grey livery!