The Greek word for firstborn (Prototokos) is found 7 times in the New Testament. It means first in rank, an heir, to have preeminence in position, NOT in origin. The other Greek word for created is Protoktisis, it is NOT used for Christ.

The word “firstborn” in the Greek is “prototokos,” and is a term of pre-eminence, and means “first begetter” or “original bringer forth”. Jesus is presented as before all things and is the Creator. Within Christianity, the Creator is separate from His creation. Creation or a creature cannot be the Creator. The position of Creator is reserved for only God of the Bible (Gen. chapter 1)

“He is the image of the invisible God, the firstborn of all creation. For by Him all things were created, both in the heavens and on earth, visible and invisible, whether thrones or dominions or rulers or authorities—all things have been created through Him and for Him. He is before all things, and in Him all things hold together. He is also head of the body, the church; and He is the beginning, the firstborn from the dead, so that He Himself will come to have first place in everything.” (Colossians 1:15-18)

The Greek word “protoktistos” means “first-created.” Since Jesus is self-existant (not created), the Holy Spirit had the Apostle Paul use the word “prototokos,” not protoktistos.

Rev.1:5: “and from Jesus Christ, the faithful witness, the firstborn from the dead, and the ruler over the Kings of the earth.” Both Col.1:15 and Rev.1:5 both clarify the meaning of firstborn by its context to mean risen from the dead eternally. Christ was not the first person raised from the dead, but He was the first raised to eternal life in the body. Which gives him headship over the human race, Since Christ is to have preeminence he is the heir of all things.

Heb. 1:5-6 states: “I will be to Him a Father, and He shall be to Me a Son”? But when He again brings the firstborn into the world, He brought him into the world AGAIN by the resurrection. Showing he is the firstborn from the dead to eternal life

He says: “Let all the angels of God worship Him.” This also shows the Son is worshipped in the same way the Father is worshiped by his creatures.

Rev 1:17-18 And when I saw Him (Jesus), I fell at His feet as dead. But He laid His right hand on me, saying to me, "Do not be afraid; I am the First and the Last. "I am He who lives, and was dead, and behold, I am alive forevermore. Amen. And I have the keys of Hades and of Death.” Only the one who can never die, who has life eternal can have these keys.

Rev.3:15: “And these things says the amen, the faithful and true witness the beginning of the creation of God.” Jehovah’s Witnesses and Iglesia Ni Christo bring this passage to people’s attention to prove Christ is the first to be created by God. But it does not say first created.

“the beginning of the creation of God hee (NT:3543) archee (NT:740) tees (NT:3543) ktiseoos (NT:2897) tou (NT:3543) Theou (NT:2282). Not the first of creatures as the Arians held and Unitarians do now, but the originating source of creation through whom God works (Col John 1:3; Heb 1:2, as is made clear by Rev 1:18; 2:8; 3:21; 5:13). (from Robertson's Word Pictures in the New Testament)

The Greek word beginning (Gr.-Arche) means He is the source and architect of creation, which actually proves the exact opposite of those who deny he preexistence before creation. If one takes this position then the Alpha and Omega (the beginning and the end) also had a beginning, for the same word is used (Rev. 1:8, 21:6, 22:16). In fact, Rev 1:8 assigns to him who is called the beginning and the end as “the Almighty.” The Scripture says the Son (word) He was in the beginning with God (John 1:2). If the Son had a beginning, then one must also say the Father did too. Then God is not preexistent to anything He created!

The first created things are in Genesis 1:1, it says the heavens and the earth. God had to make a habitat first for the creatures, angels and humanity.

Heb.1:3: “Who being the brightness of His glory and the express image of His person, and upholding all things by the word of His power.” The God who spoke things into existence as recorded in Genesis is the God who continues to keep the universe in running order.

Robertson's Word Pictures: Jesus is the image of the invisible God, the firstborn of all creation; The image eikoon (NT:1484). In predicate and no article. On eikoon (NT:1484), see 2 Cor 4:4; 3:18; Rom 8:29; Col 3:10. Jesus is the very stamp of God the Father as he was before the Incarnation (John 17:5) and is now (Phil 2:5-11; Heb 1:3). 

Of the invisible God tou (NT:3543) Theou (NT:2282) tou (NT:3543) aoratou (NT:511). But the one who sees Jesus has seen God (John 14:9). See this verbal adjective a (NT:1), the alpha privative ("not"), and horaoo (NT:3660) in Rom 1:20.

The first born proototokos (NT:4364). Predicate adjective again and anarthrous. This passage is parallel to the Logos (NT:3015) passage in John 1:1-18 and to Heb 1:1-4 as well as Phil 2:5-11 in which these three writers (John, author of Hebrews, Paul) give the high conception of the Person of Christ (both Son of God and Son of Man) found also in the Synoptic Gospels and even in Q (the Father, the Son). This word (the Septuagint and the New Testament) can no longer be considered purely "Biblical" (Thayer), since it is found in inscriptions (Deissmann, Light, etc., p. 91) and in the papyri (Moulton and Milligan, Vocabulary, etc.). See it already in Luke 2:7 and Codex Sinaiticus ('Aleph) for Matt 1:25; Rom 8:29. The use of this word does not show what Arius argued that Paul regarded Christ as a creature like "all creation" pasees (NT:3909) ktiseoos (NT:2897), by metonomy the act regarded as result)]. It is rather the comparative (superlative) force of prootos (NT:4361) that is used (first-born of all creation) as in Col 1:18; Rom 8:29; Heb 1:6; 12:23; Rev 1:5. Paul is here refuting the Gnostics who pictured Christ as one of the aeons by placing him before "all creation" (angels and men). Like eikoon (NT:1484) we find proototokos (NT:4364) in the Alexandrian vocabulary of the Logos teaching (Philo) as well as in the Septuagint. Paul takes both words to help express the deity of Jesus Christ in his relation to the Father as eikoon (NT:1484) (Image) and to the universe as proototokos (NT:4364) (First-born). (from Robertson's Word Pictures in the New Testament)

 Vincent's Word Studies Colossians 1:15 Who is the image of the invisible God, the firstborn of every creature:

The image eikoon (NT:1484). See the note at Rev 13:14. For the Logos (Word) underlying the passage, see the note at John 1:1. "Image" is more than "likeness" which may be superficial and incidental. It implies a prototype, and embodies the essential verity of its prototype. Compare "in the form of God," Phil 2:6 (note), and "the effulgence of the Father's glory," Heb 1:3. Also 1 John 1:1.

Of the invisible God tou (NT:3543) Theou  (NT:2282) tou  (NT:3543) aoratou  (NT:511). Literally, "of the God, the invisible." Thus is brought out the idea of "manifestation" which lies in "image." See the note at Rev 13:14.

In other words what was invisible of God was seen by a man called Jesus, who was the exact image. Not all understand nor believe. Why?

2 Cor. 4:4 “whose minds the god of this age has blinded, who do not believe, lest the light of the gospel of the glory of Christ, who is the image of God, should shine on them.”