Pennsylvania police lights are exclusively to be red and blue. White is optional. Possibly you saw a car with faulty lights. An agency that installs only blue runs the risk of being mistaken for volunteer firefighters, which they wouldn't do for liability reasons. With the advent of LED lights, it's becoming a shitshow, varying quality, color, intensity, placement on vehicle, etc., plus every plow jockey and construction foreman has them installed. Police tend to reuse light systems on newer vehicles to save money, possibly this could explain it? Couldn't replace red obsolete bulbs or something? Might want to call and ask that department.