Fans of old radio may know that NBC once ran two radio networks – the Red network and the Blue network. This dates back to 1926, when RCA bought out AT&T’s radio broadcasting interests, including WEAF in New York City. This complemented RCA’s 1923 acquisition of WJZ in Newark, New Jersey, from Westinghouse. Each of these flagship stations had their own affiliates, and by 1927, NBC was running two networks: the NBC Red network, which had the stronger stations and better programming, and the smaller NBC Blue network, which generally had programming with less popular appeal, including the NBC Symphony Orchestra and the Metropolitan Opera.
In the October 1942 issue of Radio Age, NBC announced that the Red network would simply be known as NBC, and the two networks would be separately managed. This was no doubt in preparation for a sale of the weaker Blue network the following year, when it became ABC.
Radio Age explains the reason for the designations:
Engineers of the American Telephone and Telegraph Company were responsible for its coinage, and not the National Broadcasting Company. In order to simplify matters the engineers used colored pencil markings to show circuit routings on their maps. Red was used for the NBC-WEAF network, and blue for the NBC-WJZ hookup. Not until some years later did NBC decide to make these two terms more widely known among the public, and such a campaign was started on the air and in advertising and promotion matter.
These names caused NBC some concern from listeners who saw a more ominous purpose and a silent menace behind the naming:
The publicizing of the term soon brought irate letters from less enlightened listeners. They began to accuse NBC of a lack of patriotism and base designs on the American way of life. Previously these listeners had accused NBC of making the radio waves play strange melodies on their bed-springs, and felling blackbirds while in flight.
Wrote one friendly correspondent who did not view the matter with alarm: “The minds of some people are very easily swayed and I know for a positive fact that your slogan has been grossly misinterpreted. We all know that NBC has been and always will be one hundred per cent American. . . .”
You can read the whole story in Radio Age, here on the Media History Digital Library website. The original article is http://www.archive.org/stream/radioageresearch194245newyrich#page/n27/mode/2up
This article discusses how the Blue network was managed as a separate network by NBC: