Technically the 2.5 liter 4 cylender Altima's do not have dual exhaust. There is just a single pipe that comes off the manifold and it splits into a "Y" just before the rear bumper. Hence the 2 cutouts.
The 3.5 liter V6 does have true dual exhaust.
Thanks! Too bad you weren't asking the questions because NG's guest probably knows a lot like you do. We have the transcript already. I thought this guest was well worth listening to (and he would know the factory colors for that year and he guesses it is silver):
http://transcripts.cnn.com/TRANSCRIPTS/1605/23/ng.01.html
"GRACE: ......Steven Becker joining me right now, vehicle ID expert with Robson Forensics. Steven, we`ve given you this information. What can you tell about this vehicle?
STEVEN BECKER, VEHICLE IDENTIFICATION EXPERT (via telephone): Hi, Nancy. The vehicle`s actually quite identifiable. It`s interesting there`s so many features that are noticeable in this grainy black nighttime, grainy video footage. But you can clearly figure out what type of car this is.
[20:05:00]GRACE: Well, what can you tell us? Break it down.
BECKER: Sure. The main features, you can see -- if you look at the lower portion of the bumper,
you`ll see dual exhaust pipes, very unique feature for a four-door sedan. You can also see that this is a four-door sedan. You can see the door handles on the side.
You`ve got a V-shaped trunk lid with the license plate in the center of the trunk lid, not on the bumper. There`s also a bumper sticker below the license plate that`s identifiable. You can even make out the emblem and the shape of the emblem indicating that it`s a Nissan. And then there`s a piece of chrome trim above the license plate that clearly identifies the year of the Nissan in the video. Also, the...
GRACE: Whoa, whoa! Wa-wait! Wa-wait! What year is it? Can you tell what year it is?
BECKER: Oh, definitely. This is a 2010 to 2012. You can`t narrow it down more than that because they didn`t change the rear end of the vehicle much between those two years. But what you can tell is that, like in the 2015 or one of the newer ones, the chrome trim is much, much wider. In other words, it would definitely show up and you`d identify it differently from the incident vehicle. The older ones, like the 2007 and such, there is no chrome trim of the license plate. And the geometry of the bumper is different, as well.
GRACE: OK. In a nutshell, Steven Becker, vehicle ID expert with Robson Forensics, if you had to put money on it, what would you say this car is -- make, model, year, color, anything you can tell me?
BECKER: Again, it`s a 2010 to 2012 Nissan Altima. It`s light in color, and
I would say more likely than not silver. ..."