That’s my understanding, also. They also have other markings on a few units they are testing for visibility.From what I've heard, it has to do with a study that Virginia Tech is doing in regards to the visibility of blue vs. red lights at day time and night time. I'm not sure how accurate that information is, it's just what's been mentioned by a couple of Troopers when I mentioned it the other day.
While any color LED is certainly brighter than it's halogen or strobe counterparts, there are still marked differences in red and blue in the daytime and nighttime. It's one reason that I hope that one day the legislature will let fire apparatus run a single blue light to the rear like has been adopted in another of other states.So it would seem to me that with the use of LEDs, visibility wouldn't be as much of an issue as it would have been in the past.
New York changed their laws in 2007 IIRC allowing rear-facing blue lights on emergency vehicles for increased visibility.In New York, blue is solely for vounteer fire fighters.... green is for volunteer ambulance/EMTs. Emergency vehicles have red or red and white only, although I have seen blue lights on NYPD units (just one light out of many).