Once you were alienated from God and were enemies in your minds because of your evil behavior. But now he has reconciled you by Christ’s physical body through death to present you holy in his sight, without blemish and free from accusation— if you continue in your faith, established and firm, and do not move from the hope held out in the gospel. This is the gospel that you heard and that has been proclaimed to every creature under heaven, and of which I, Paul, have become a servant. –Colossians 1:21-23
When I first read this, I thought, ‘so it’s obvious that those who are not established and firm in their faith and their hope in the Gospel will no longer be without blemish, but is he suggesting that they will also no longer be reconciled with God?’
But as I look at it more, I think it’s pretty simple to say that they key words here are “reconciled to”. For if we step away and begin behaving as we once did, are we not sinning? And doesn’t sin separate us from God, and so if separated, do we not again need to be reconciled?
As for the topic of salvation, I don’t believe this passage touches on it.