Colbert has hosted Star Wars Episode IX panel earlier today. The event was held in Chicago (the video is here, if anyone is interested, but you should skip to 19 minutes mark, when the event actually starts).
And on Sunday he will be in London to moderate Becoming: An Intimate Conversation With Michelle Obama in promotion of her memoir, Becoming Michelle Obama. As a result, Monday's show will be rerun.
Edit: Actually, Monday's show will not be rerun. From CBS Press Express, the guest are: Molly Shannon; Gary Cole; musical performance by Paul Simon; Flipped interview with Trevor Noah.