Not completely sure on this, but I wonder if some advertising sign colour preferences were based on how people interpreted colour meanings during that period of history – red and royal blue are regal colours that may have subconsciously communicated trust, stability, loyalty…
Also if you look at military uniforms of the period Red and Blue colours are in the majority. There may also be a cultural connection as well as green is a lucky colour in the Emerald Isle, but in England you were always told not to buy a green car as they are unlucky. Also Ireland telephone enamels were usually green background as in England they were a dark blue background.
Any marketing colour historians in the group?
Just my 2p worth ;-)