CBS’s Late Show With Stephen Colbert kicked off with an easy ratings victory Tuesday night, attracting a solid first-night audience of just over 6.5 million viewers, according to preliminary Nielsen data. Not counting David Letterman’s farewell week, Late Show earned its biggest audience for a Tuesday show since 1995. More important, Colbert’s first outing did very well with viewers under 50, delivering a 1.4 rating in the advertiser-friendly demographic — nearly three times the demo ratings David Letterman was averaging in his final season. Not unexpectedly, Colbert beat both of his broadcast rivals at 11:35 p.m., finishing well ahead of both Jimmy Fallon (2.9 million; 0.9 in adults 18–49) and Jimmy Kimmel (1.8 million; 0.4 in adults 18–49). The good news for Fallon, as an NBC rep noted, was that Colbert’s arrival didn’t impact Fallon’s Nielsen numbers among younger viewers at all: The Tonight Show host matched his summer ratings average in the demo. It should be noted that ratings for Colbert were probably hurt just a bit by the fact that the show ran longer than an hour, and that it debuted on a night when CBS didn’t do much in the ratings in prime time. Still, Late Show under Colbert is off to a solid start — and Fallon has no reason to be concerned about his audience so far either.