What kind of talk show host will Stephen Colbert be once he assumes the late night mantle at CBS? His appearance Tuesday on “The Late Show with David Letterman” offered few clues. But there was something subtle I couldn’t help noticing: Colbert’s choice of eyewear.

Gone were his standard rimless glasses, replaced by darker, more prominent frames. It seemed like a small, almost subliminal attempt to distance himself from the blowhard pundit “Stephen Colbert” character he has played for nearly 10 years on Comedy Central.

Was it a sly way of signaling that he was out of costume, so-to-speak - as he will be when he takes over the job from Letterman? Or maybe I’m just reading too much into it. Perhaps the guy just felt like wearing a different pair of glasses.

(Meanwhile, over on “The Colbert Report,” dressed in the same suit and tie, Colbert was back to his rimless glasses and interviewing author George Will about his book on Wrigley Field’s 100th anniversary and asking: “Do you love the Cubs, or is it an abusive relationship you can’t get out of?”)

Coming not quite two weeks since the official announcement that he would replace Letterman, Colbert’s appearance on the show was loose but unquestionably focused on the upcoming changing of the guard. “What is the family doing now?” Letterman asked. “I’ve got my show for the rest of the year,” Colbert said, “and then - and then, I don’t know, when you are you leaving? I don’t know, I should have asked!”

Both Letterman and Colbert share a Midwestern sensibility (Letterman’s honed in his home state of Indiana; Colbert’s during his decade-plus in Chicago, first at Northwestern and later at Second City) and it was evident in the following bit of self-deprecating one-upmanship.

Here’s Letterman expressing his pleasure at Colbert’s hiring: “Paul and I have been doing this for a long, long time, and they could have just as easily hired another boob like me. But they didn’t. They hire a guy -“

Colbert: “They hired a boob like me.”

Letterman: “No, no, no, no.”

Colbert: “Every boob is like a snowflake, Dave. We’re all unique in our own way.”

Whether or not we got a better glimpse of Colbert as future CBS late-night talker remains an open question. It will be about a year or so before he takes over the slot. Letterman didn’t bother asking about Colbert’s plans for the show, and that’s just fine. The man has plenty of time to figure things out.

In place of family anecdotes (or the unexpected piece of theatrical whimsy, as when Colbert appeared on Letterman this past December dressed like an extra from a third-rate production of “A Christmas Carol”), Colbert offered up a pair of stories that related back to Letterman.

The first concerned an internship Colbert was offered while in college and Letterman’s show was still on NBC. It was Colbert’s girlfriend at the time who actually had an interview to work on the show. Colbert was just tagging along to keep her company but chatted with the staff anyway. End result: He was offered the position; she wasn’t. That was the end of the relationship. (Colbert didn’t take the gig anyway because: no pay.)

A decade later, after several years performing in Chicago’s sketch and improv scene, Colbert had moved to New York and was in need of work.

“In 1997, you guys were looking for writers and I was gainfully unemployed. I was unemployed at a professional level. My writing partner and I, Paul Dinello” - whom Colbert met and performed with at Second City - “we submitted a packet to you guys, and y’all didn’t call for four months.”

When the show finally did express interest, Colbert, Dinello and Amy Sedaris had already moved on to their show “Strangers with Candy.” But Colbert brought along the Top Ten list he and Dinello submitted, and I’ll wager it was the real deal for no other reason than its completely out-of-context Christmas theme: Top Ten Cocktails for Santa.

Look, I don’t think anyone is worried that Colbert will be recycling Letterman’s bits when he jumps to CBS, but it wasn’t a bad idea to have him essentially assume a Letterman-esque pose for a moment, complete with the standard graphic intro: “Wait a minute,” Letterman said, “he doesn’t get that yet!”

For what it’s worth, the list was just the right amount of dark and funny, including No. 9: “Mama Said Nog You Out - 3 fingers of egg nog, one finger of ether” and No. 6: “Scrooge Driver - grain alcohol and regret.”

“You look good. You look right at home,” Letterman said to his heir apparent, and both men couldn’t have seemed more at ease with the way this has all played out.

“Ladies and gentlemen,” Letterman said in his wonderfully formal folksy way. “Here he is: It’s the new kid.”