The Colour Strike was an industrial action by technicians at all ITV companies from 13 November 1970 to 8 February 1971 who, due to a pay dispute with their management, refused to work with colour television equipment. At that time ITV had recently switched to colour transmissions, requiring the individual companies to invest heavily in new equipment. Early colour television studio cameras consisted of four tubes to relay the picture: three were receptive to colour with the fourth providing a high-resolution monochrome image which was still required as many viewers still watched on monochrome receivers. The final colour picture was created by combining the chrominance and luminance signals, but the technicians simply switched off the colour tubes whilst this dispute took place. This meant that even though colour equipment was available, all shows were recorded and broadcast in monochrome, thus denying the ITV companies the ability to sell airtime at the higher value that colour transmissions dictated. In some film sequences for location shots in these programmes, the colour signal from the telecine machine had to be switched off in the vision mixing desk before being recorded to tape, but this was partly unsuccessful, leading to some film sequences being recorded with an odd array of pale colours. This is prominent in the second series of Hadleigh, for example. The first Coronation Street to be broadcast in colour was transmitted on 3 November 1969, but due to the strike, some 1970–71 episodes, including the one featuring Valerie Barlow's electrocution, were recorded in black and white. The last monochrome edition was shown on 10 February 1971, although the episodes transmitted on 22 and 24 February 1971 contained black and white film inserts. All of ITV's programmes were broadcast in black and white throughout this period, including scheduled repeats and regional programmes. The strike was called off on 2 February 1971 with all colour production and transmissions resuming on 8 February except for some ITV regions continuing to broadcast in black and white until the following dates: Westward Television, Border Television, Grampian Television and Channel Television. There was also a short dispute two years later in early 1973; this affected both BBC channels as well as ITV.
