I'm not certain about the colour of the fire extinguishers, but there's a good chance that American units were red.
During WW2, and for some time after, RAF fire extinguishers, of various types, were normally the bare metal, a brass colour, although by the end of the war, the 'emergency' colours were starting to be seen, with jettison handles and other 'emergency' equipment, such as axes, fire extinguishers etc, being painted red.
Other colours, more cautionary, such as handrails and the outlines of emergency exits etc, were yellow.
Standardisation didn't really happen until the mid 1960's, when the various types of fire extinguishers had an indentifying colour, eg, cream for foam, mid blue for dry powder, mid green for BCF etc etc., although even then, and still today, 'commercial' units could be stainless steel with a label of the appropriate colour - as much use as a chocolate tea pot when trying to find the right piece of equipment in a smoke and low light environment !