High Quality Content by WIKIPEDIA articles! Blues and twos is a colloquial British term that refers to the emergency vehicle equipment of combined flashing lights as well as sirens that the emergency services in the UK and Ireland use when responding to an incident. The origin of the phrase comes from the fact the lights are usually blue and the traditional siren was a two-tone horn, although now most emergency services use combinations of other modern siren sounds. Some emergency services are still using traditional two-tone horns; these include South Yorkshire Fire and Rescue Service, (including their new Scania appliances); Oxfordshire Fire and Rescue Service; Dublin Fire Brigade; Greater Manchester Police; and, because of their age, many Royal Air Force, Royal Naval Air Service and Civil Defence fire-fighting vehicles are still fitted with compressed air two-tone horns.