What is the best way to tell if a Crown Vic is a cop?

[Way2fasts]

There is one way from a distance that you can spot that i do not think anyone has said yet, it seems to me from my driving that the leo's stick out like a sore thumb, in arizona they are only three colors white, dark blue, or a really light blue. Not once have i seen any other color, while most of the crown vics out there you never see in dark blue, and rarley do you see any in the light blue

[Way2fasts]

but that being said i do not know how reliable that is with other states, so dont try it unless you are sure the cops dont have other color cars