On a recent Monday night, Stephen Colbert was about as high atop the Ed Sullivan Theater as one can be, looking out over the 200 or so employees of his CBS “Late Show” who had gathered for a roof party as he stood on a staircase with a megaphone in hand.

In a few moments, Mr. Colbert’s bandleader, Jon Batiste, and his fellow musicians would guide the crowd in joyful gyrations while a far-off camera swooped in — all for a few seconds of footage that will appear in the opening credits of this reinvented “Late Show” when it makes its debut on Tuesday.

Throughout the evening, Mr. Colbert had been slipping in and out of the festivities, wearing a steel-blue suit and shimmying with co-workers. Now, from his elevated perch, he was instructing his colleagues on where to stand and how to dance, and he seemed just as comfortable to be in charge of the revelry as he was participating in it.

“Follow the sound of my voice,” he said, its trademark archness reverberating in the warm twilight air. “Go towards the waving man. This is the magic time.”