Contradiction with Matthew 6:5
Matthew 6:5 suggests praying in secret to God, which could be seen as contradicting thanking God together with others as in Colossians 1:3.
Matthew 6:5: And when thou prayest, thou shalt not be as the hypocrites [are]: for they love to pray standing in the synagogues and in the corners of the streets, that they may be seen of men. Verily I say unto you, They have their reward.
Contradiction with Luke 18:11
The Pharisee in Luke 18:11 thanks God arrogantly, potentially contrasting with the humble, collective gratitude in Colossians 1:3.
Luke 18:11: The Pharisee stood and prayed thus with himself, God, I thank thee, that I am not as other men [are], extortioners, unjust, adulterers, or even as this publican.
Contradiction with James 4:3
This verse states that prayers may not be answered if asked with wrong motives, which could conflict with the assumption of mutual worthy prayer in Colossians 1:3.
James 4:3: Ye ask, and receive not, because ye ask amiss, that ye may consume [it] upon your lusts. [lusts: or, pleasures]
Contradiction with 1 John 3:20
This verse implies God knows everything in our hearts, which may present a contradiction if taken to suggest that expressing thanks (as in Colossians 1:3) isn't necessary.
1 John 3:20: For if our heart condemn us, God is greater than our heart, and knoweth all things.
Contradiction with Ecclesiastes 5:2
This verse advises against being hasty in prayer, which could contrast with the frequent and communal thanksgiving in Colossians 1:3.
Ecclesiastes 5:2: Be not rash with thy mouth, and let not thine heart be hasty to utter [any] thing before God: for God [is] in heaven, and thou upon earth: therefore let thy words be few. [thing: or, word]