In 1968 the first of the grey Police cars arrive and the Police vehicles remained grey , with a single red flashing light until 1978, when the new style patrol cars rolled out with the dual blue flashing lights.
The blue flashing lights was a departure from the conventional emergency vehicles in that Police cars do not have sirens.
It was important, therefore, for police cars to be able to be visually seen in heavy traffic and not to be confused with numerous brake & indicator flashing lights, as can be seen in heavy traffic.
The blue, of course, aligns the New Zealand Police with other countries of the World, thus standardizing emergency colours.

At the time of this article Hawera’s Police fleet consisted of two white patrol cars and one unmarked car.

Article from “The History of a Small town Police Station” Hawera Centennial 1982