no offence intended to the initiator of this post but... Even if you knew every make, model, and color of every unmarked/ undercover cop car out there it ain't gonna help. I say that because there are only two times when you spot an undercover cop car 1) when you've passed it doing what ever it was you weren't supposed to be doing, and 2) when its pulling you or your freinds ass over for doing what ever it was you did. And both of those times are FAR TOO LATE to be spotting an undercover car.
That is unless your passenger wants to drive around with a set of binoculars.