lenaitch
Senior Member
It has nothing to do with conspicuity. LEDs now enable most colours to be generated right from the diode ('bulb') rather than created by a lens or filter. This allows an almost unlimited range of configurations simply by rearranging modules rather than requiring manufacturers the to provide different enclosures. It also eliminates the need for internal lens under the enclosure. it also allows the output to be tailored to the colour, since different colours have different electrical efficiencies. This was always the problem with blue when everything was incandescent; the blue lens absorbed so much light from the standard bulb that they were very ineffective particularly in daylight. Having a blue lamp that produced a light with the same effective illumination as a red required a more powerful bulb.The new lightbars are clear now. They give off a more visible flash when activated, but they have no colour while turned off. Another way they've gone more inconspicuous. In some other cities to deal with the blank LED lights, they may have a partial red and blue solid glow at all times, to be better seen.
Emergency vehicle lighting varies by jurisdiction. California requires emergency vehicles to have one steady burning red lamp; a requirement which long pre-dates LEDs.
As an aside, folks seem to be wound up about grey cars. Best as I can find out, TPS dropped overall grey cars in 2016 in favour of grey with four white doors (not counting subdued markings/plain cars).