Colossians

Paul does not refer to his time in prison in the book of Colossians.

From the context, it seems like he has never met the church of Colosse.

The central thrust of the letter is to dissuade people from feeling that they are forced to observe various rules and regulations.  These include the dietary rules, the Sabbath and holiday observance, and of course, circumcision.  These rules were all nailed to the cross with Jesus.

Chapter 3 begins a layout of the Christian morality.  These include sexual purity, truthfulness, honesty, and when one works, work as if one is working for God.

Colosians also has some interesting statements.  It seems that Barnabas has a cousin named "Mark".  We also find out that "Luke" is a doctor.