Why Colossians? Why Now?

Mainly because many people people think that the Bible is negative, as though it were all about the "Thou Shall Nots". It isn't. And if any one writer in the Bible is singled out as having a negative message, it would be Paul. But here, at least, Paul demonstrates a positive message. He doesn't just tell what not to do. He also gives advice about what one should do. For instance, "Put on therefore, as the elect of God, holy and beloved, bowels of mercies, kindness, humbleness of mind, meekness, longsuffering; forbearing one another, and forgiving one another, if any man have a quarrel against any: even as Christ forgave you, so also do ye. And above all these things, put on charity which is the bond of perfectness." (Col. 3:12-14) Or Col. 3:15b: "Be ye thankful."

No negativity in the message here, just positive advice. No threats -- "Be thankful or else." Just words of wisdom to help the reader, not to hurt. That's why Colossians.