[Renald Showers states, (Israel My Glory periodical, pp. 28-29, "THE FOUNDATIONS OF FAITH, The Eternality and Pre-Existence of Christ")]:

"In Colossians 1:15 the Apostle Paul referred to Christ as 'the firstborn of all creation.' Some individuals and groups insist that this designation indicates that Christ was the first part of creation that God brought into existence. They claim that Paul was teaching that Christ is a created being, that He had a beginning in time and therefore is not eternal.

Does the expression 'the firstborn of all creation' mean that Christ was the first thing created? No, it does not. Paul was not saying that Christ is a created being. Several things prompt this conclusion.

First, Paul wrote Colossians to refute a heresy (Gnostic Judaism) that taught that Christ was part of creation.

Second, the idea that Christ was created is contrary to the context of Paul's reference to Christ as 'the first-born of all creation.' The context teaches that Christ created everything that has been created (vv. 16-17). Thus, F. F. Bruce wrote, 'The context makes it clear that this title is not given to Him as thought He Himself were the first of all created beings; it is emphasized immediately that, far from being part of creation, He is the One by whom the whole creation came into being' (Commentary on the Epistle to the Colossians in The New International
Commentary on the New Testament
, p. 194).

Third, there was a Greek word (protoktistos) had two connotations: priority and sovereignty. Priority had two possible subconnotations: the first part of something or existence before something. The context of the word determines which sub-connotation is intended. The Colossians 1 context demands the sub-connotation of existence before something (vv. 16-17). Thus, when Paul referred to Christ as 'the first-born of all creation,' he was teaching that Christ existed before and is sovereign over all of creation. F. F. Bruce stated, 'What the title does mean is that Christ, existing as He did before all creation, exercises the privilege of primogeniture as Lord of all creation, the divinely appointed 'heir of all things' (Heb. 1:2). He was there when creation began, and it was for Him as well as through Him that the whole work was done" (Ibid).