Colossians 1:9  “…ye might be filled with the knowledge of His will…”

Colossians 1:12  “Giving thanks unto the Father, which hath made us meet to be partakers of the inheritance of the saints in light:”

Colossians 1:16  “…all things were created by Him, and for Him:”

Colossians 1:26-27  “…the mystery which hath been hid…but now is made manifest…the glory of this mystery…Christ in you, the hope of glory:”
I wish Paul didn’t ramble on so much, but that may be the way the Greek works.  Appears the mystery is salvation by Christ.  That God intended His salvation for all men, Jew and Gentile.  In other places, Paul speaks of how it has been revealed that God’s plan was to save all of mankind, not just the Jews as it appeared.  Jews missed the point of their calling.  Wasn’t just to save them, but the message of God’s love and His desire for mankind’s redemption and reconciliation was for all men.  It was just given through the Jews as fulfillment of His promise to Abraham.  And it was completely realized in Christ.

Please feel free to comment or post questions.  Thanks for reading!