Town police colours

scottdd2

I just picked up a neat little copy of #6632 Tactical Support Truck and started to wonder why the majority of Town police vehicles were white and black or vice versa. There's a grey van in #6598 and black and grey in #6332 and #6328 but that's it. I know black and white is/was big in the US but I would have thought at that stage the colours would have been modelled more on EU vehicles (based on the fact that every emergency vehicle had blue lights) and I couldn't find too many real life examples in that colour scheme. 
This continued on into 2003 for the World City line.
In the City line you start to get blue and white with a couple of sets even being available in either black or blue versions, #7236 #7235 and #7245.
Forest and Mountain then went majority blue and white.
Yet in the fire or ambulance lines they remain pretty much as they started with only changes to the highlight colour.
The ambulance in #60330 and a couple of exceptions in fire with #20002 in yellow and #6440 in majority white are the only ones that really deviate from the standard.
Could we see a lime green fire appliance or all yellow ambulance in the future?