Colossians is a book that was written by the Apostle Paul to encourage the believers in Colosse and Laodicea; to teach and clarify the doctrine of Christ's Deity. There was a new doctrine that was making inroads at these two cities, one that blended all the religions of the day into a synchronicity of spirituality. It left Christ as a human that served this world as a prophet. They taught that Christ alone could not bring salvation.
Paul clearly proclaims Christ as Sovereign in order to refute this false doctrine.
James is about growing in maturity as a believer. A grown-up believer displays wisdom, self-discipline, and commitment to a consistent walk with Christ.He or she is determined to obey God regardless of the cost and to seek regular nourishment from His Word.