Actually, speed cameras can be any colour; what happened a few years ago, was that the police used to operate the cameras exclusively, and all of the money went to the government. However, in around 2003, (i think), the government introduced a thing they called "hypothecation", which meant that whatever money the camera had made was set, and if the camera then made more money in subsequent years, the police were given that "extra", the money above what it had previously been received. But to be eligable for the money, the police had to paint the cameras which were eligable, under the scheme, yellow. This meant that the police were then able to pay for the policing of the cameras from the money they were able to generate; whereas befor hypothecation came in, they paid for the policing out of thei own budget.
