It is fairly common to see brake hoses (on models) that have been painted.
What I think is correct for our era is that the hose itself (the rubber part)
should be DULL black (rubber) - with considerable road grime that is often
almost brown, and the fittings (valve and hose end) should be oxidized rust
(most of the time), black (some times - if that particular RR painted theirs ...
but still dirty), and ... rarely ... white. Additionally,
I know that some RRs used a band of metal around the hose near the
end that is sometimes painted white, red, or (later, past our era) silver.
Were these bands even there in the post WW-II era?
What I do not think is 'ever' (never say never) right is that the metal
fittings are silver.
Cannot find anything on a metal label.
However, 1953 Car Builders Cyclopedia has this definition:
Air Brake Hose Label. A label of red or white rubber vulcanized to the air-brake hose near one end. In the label is to be branded the initials or name of the railroad or other purchaser; the name of the manufacture; the date of manufacture; the hose serial number; and the monogram of the mechanical association.
Similar requirements date back to 1905 or earlier.