blues and twos

Etymology
Originally 1960s police slang, from the blue colour of the lights and the two-tone sound of the siren. Publicised by Blues and Twos, a documentary series broadcast on ITV from 1993.

Alternative spelling

 * blues-and-twos

Noun

 * 1)  The flashing lights and loud siren of an emergency vehicle.

Adverb

 * 1)  [of an emergency vehicle] with the blues and twos switched on