In the “Our Town” scene in the first Cars film, there’s a teal tow truck with buck teeth at Flo’s. Could this be Mater? Because the scene takes place forty years in the past and it could be argued that present-day Mater is covered with rust and has no paint color anymore.
Yes, it’s confirmed it’s indeed him. 
A bit of his original blue color even still remains on his sides in his modern form.
Confirmed by who?
Well, for example, the Cars Finder game as well as Mattel’s diecasts identify the tow truck as Mater.