The Lord will confirm believers to the end in a state of blamelessness, even to the day of our Lord Jesus [1 Cor. 1:8]. This means that our being counted righteous is something God will not allow to be changed; it is a work dependent on His power and faithfulness only [1 Cor. 1:9].
However, when we look at the same word "blameless" in Colossians 1:21-23, a different reality is presented, where we see that if we continue in the faith, grounded and steadfast, and are not moved away from the hope of the gospel, He will present us holy, blameless, and above reproach in His sight [Col. 1:21-23]. Because this presentation is conditional based upon a continuing faith, these are two entirely different realities in the Scriptures [Rom. 11:22]. Understanding this distinction will save us from much confusion and faulty interpretations!
The first is a positional blamelessness that took place at our conversion via the Gospel, which is a guaranteed presentation of our legal status, sustained entirely by the grace and fidelity of God [1 Cor. 1:8]. Paul was encouraging the immature believers in the assembly at Corinth that despite their spiritual struggles, God will keep them in a state of blamelessness even until the day Jesus returns [1 Cor. 1:4-8]. For how can we ever be eternally condemned when it was Christ who died for our sins [Rom. 8:34]?! And it was God who counted us righteous in Him [2 Cor. 5:21]! Hallelujah!
Furthermore, the second reality relates directly to our spiritual maturity because of our reconciliation to the Father, which is an approved presentation of our progressive growth and experiential holiness, conditioned on our persevering reliance upon Him [1 Cor. 2:6-7] and holding fast to sound doctrine and the hope of Christ [Col. 1:22-23]. We see throughout Paul's letter that He had a burning desire for them to mature and fulfill the will of God in Christ Jesus [Col. 1:9-11]. He passionately labored so that He might present every individual perfect and fully assured in all the will of God [Col. 1:28, Col. 4:12].