The Greek prototokos can mean first in rank, supremacy, preeminence not first in time:

• Genesis 41:51 Manasseh is called “firstborn” and Ephraim is called “second.” But in Jeremiah 31:9, Ephraim is called “firstborn” because it is was Ephraim who now had the preeminence or supremacy, and not Manasseh.
• Exodus 4:22, Israel is called “firstborn” and certainly they were not the first nation created, but as God’s people they had preeminence.
• Psalm 89:27, David, because of his status (i.e., his preeminence), is called “firstborn” and he was technically “last born” (note: in the LXX, both passages have prōtotokos).

Even the Watchtower acknowledges the correct meaning of the term by admitting:

David, who was the youngest son of Jesses [sic], was called by Jehovah the “first-born,” due to Jehovah’s elevation of David to the preeminent position in God’s chosen nation (Aid to Bible Understanding, 1971, 584; emphasis added).

Colossoans 1:15

If Paul wanted to convey that Jesus was “first-created,” he certainly could have used the word prōtoktistos literally meaning, “first-created” to do so (as in 2 Cor. 5:17). Hence, Jesus was not the first-creature, rather He was the Creator of ALL THINGS (cf. John 1:3; Col. 1:16-17; Heb. 1:2, 10-12), whereby in everything He has supremacy (cf. Col. 1:18). Points to remember:   

• In the context of Colossians, “firstborn” (prōtotokos) means supremacy or preeminence—Christ as Creator is preeminent over creation (cf. Exod. 4:22 and Ps. 89:27). 
• Even the Watchtower acknowledges the correct meaning of “firstborn” (“preeminent position”).
• If Paul wanted to express that Jesus was created, he could have used prōtoktistos (“first created”).

The term translated “firstborn” denotes Jesus as “having special status associated with a firstborn” (BDAG, Bauer, A Greek-English Lexicon, 894). Biblical scholar Robert Reymond extracts the true significance of the term:

Paul’s intention behind his description of Jesus as “the Firstborn of all creation” is a universe away from the Arian interpretation of the JWs that would insist that the word shows that the Son was the “first” of all other created things; the entire context demands the term is to be understood in the Hebraic sense as an ascription of priority of rank to the firstborn son who enjoys a special place in the father’s love. (Reymond, Systematic Theology, 251).