That is tinted glass...that is, it is basically colored glass...it is part of the glass itself. It is NOT like aftermarket tint. Aftermarket tint is a film they put over the inside surface of your glass.
With a lot of aftermarket tint you will see bubbles after awhile. My Son does not like the tinted glass, it is hard to see the sites from the back window, of course he is pretty much stuck with it.
I have a 2nd gen and the factory tint (front driver and passenger) is very very weak. They are currently sporting their second round of aftermarket tint film - now if I could just get a line on some replacement gaskets for the rear doors - that'd be great..
Factory tinting is usually done by adding pigment to the glass, making it part of the glass. They offer better UV protection and heat rejection, plus they're covered by the vehicle's warranty. Aftermarket tinting gives you more customization options in terms of shade and darkness levels, though.