As same as many other countries, Japanese police cars are vehicles manufactured in Japan. Then, the most significant difference between other nations' police cars and Japanese one is that Japanese police car(except marked cars) is always painted in black and white colors.
Many police cars in Europe are having painted in blue color and hard to see black one. It is told that Japan introduced black due to the road situation. Many roads were unpaved and did not want to be visibly dirty. Therefore they painted black on the lower parts of the vehicles.
However my opinion is different. Japanese consider guilty and innocent in colors. Guilty is black and innocent is white. Then, police is the first jurisdiction to make an arrest. Therefore they kept these colors even the roads are mostly paved now.
The emergency vehicle lighting is always red. The vehicles which can use red color for the rotating light is limited only for emergency vehicles.