JWs argue that the Father is not called Firstborn, well that's false:
"The Greek for "firstborn" is prototokos, which means "preeminence" and "eternal preexistence," according to Greek lexicons. It does not mean "first-created." Apart from being untrue linguistically, this heretical interpretation is contradicted in the next two verses, which inform us that Christ "created all things," and that He "is before all things." The Hebrew usage of "firstborn" is also instructive, since it illustrates its meaning as "preeminent." David is called "firstborn" in Ps 89:27, not because he was the literal first child of Jesse (for he was the youngest), but in the sense of his ascendancy to the kingship of Israel. Likewise, Jeremiah 31:9 refers to Ephraim as the firstborn, whereas Manasseh was the first child born (Gen 41:50-52). The nation Israel is called "my firstborn" by God (Ex 4:22). The Jewish rabbinical writers even called God the Father Bekorah Shelolam, meaning "firstborn of all creation," that is, the Creator. This is precisely how St. Paul uses the "firstborn" phraseology in Col 1:15.
If Jesus created "all things," then He Himself cannot be a thing (i.e., a creation); ergo, He is not created, but eternal. For this very reason, Jehovah's Witnesses (with no justification in the Greek text whatever), add "other" to the passage, in order for Jesus to become a creation, as they imagine, according to their Arian heretical views. Mormons (though not the Book of Mormon) also deny that Jesus was eternal and immutable, so they set forth some of the same fallacious and unbiblical arguments towards that end. As for being "in the beginning" with the Father, this, too, is in an absolutely unique sense, not applicable at all to created human beings"
Clarke's Colossians 1:15 Bible Commentary:
"The first-born of every creature - I suppose this phrase to mean the same as that, Philippians 2:9 : God hath given him a name which is above every name; he is as man at the head of all the creation of God; nor can he with any propriety be considered as a creature, having himself created all things, and existed before any thing was made. If it be said that God created him first, and that he, by a delegated power from God, created all things, this is most flatly contradicted by the apostle's reasoning in the 16th and 17th verses. As the Jews term Jehovah בכורו של עולם becoro shel olam, the first-born of all the world, or of all the creation, to signify his having created or produced all things; (see Wolfius in loc.) so Christ is here termed, and the words which follow in the 16th and 17th verses are the proof of this. The phraseology is Jewish; and as they apply it to the supreme Being merely to denote his eternal pre-existence, and to point him out as the cause of all things; it is most evident that St. Paul uses it in the same way, and illustrates his meaning in the following words, which would be absolutely absurd if we could suppose that by the former he intended to convey any idea of the inferiority of Jesus Christ."
Let's see this in the Talmud:
"“You shall redeem every firstborn of your sons. They shall not appear before Me empty-handed.” If someone has the good fortune to be a firstborn this is a true distinction. To some degree he shares this distinction with G’d Himself Who is also “a first in the universe.”" (Shemot 34:20)So when the apostle Paul called Jesus "the firstborn of creation", it rhymed with Jewish phraseology, in which God was called "firstborn of the world" ('bekoro shel olám' - firstborn-of-the-world; or 'qadmono shel olam'-First-Primordial-of-the-world), the general idea is clear: the Jesus is above all of creation.
"Bekoro shel olam" (בכורו של עולם) translates to "the firstborn of the world," and it's a term used to denote someone or something as the primordial or foremost of creation.
"Qadmono shel olam" (קדמונו של עולם) translates to "the Ancient One of the world" or "the Primordial One of the world." In Jewish thought, particularly in Kabbalistic literature, it is often used to refer to God as the Eternal and Primordial Being who precedes all creation.
Hence the term "בכורו של עולם" (bekoro shel olam) in Hebrew translates to "the firstborn of the world," while "πρωτότοκος πάσης κτίσεως" (prototokos pasēs ktiseōs) in Greek translates to "the firstborn of all creation." These term essentially mean the same thing. Both refer to the concept of the "firstborn" or "preeminent" one of all creation or the world. In Christianity, the Greek phrase is used in the New Testament (Colossians 1:15) to describe Jesus Christ, emphasizing his preeminence. The concept of "firstborn" as a special status can also be found in Jewish thought, with the Hebrew phrase carrying the idea of being the first or preeminent one.
Paul makes several key statements about the Messiah: "The firstborn of the world." He continues by saying that through Him, all things were made; visible and invisible. Everything was created by Him and for Him. He is before everything, and everything subsists in Him. The overall idea is clear: the Messiah is above all creation.
When the apostle speaks of the "firstborn of the world" (v.15), he is alluding to the preexistence of the Messiah as God. In Hebrew, it is said "Bekoro shel olam" ("Firstborn of the World"), and it was used in Jewish literature to refer to God. Bahiá ben Asher (13th century), a disciple of Rashba (considered an extraordinary rabbinic authority), in his commentary on the Torah, says of God: "He is the firstborn of the world." In his commentary on Exodus 13:2, Bahiá again refers to God as "the firstborn," interpreting this text as "consecrate to me every firstborn."
Thus, Paul, fully immersed in his people's culture, when referring to the Messiah with these terms, native to Judaism, is alluding to the preexistence of the Messiah as God -- this fits perfectly with the context; everything was created by Him and for Him. He is before everything, and everything subsists in Him. There could not be a more explicit statement that the universe was created by the Messiah than this one.
These were expressions specific to the Jewish people that could be immediately recognized by the Jewish community members of the Second Temple period. What must certainly be excluded is that the Messiah, by being considered as the "firstborn of the world," should be included among creatures.
He is not the first of creation or the first creature that God made because, as v.1.16 says, everything was created by Him, so He cannot be a creature. He cannot, with any propriety, be considered as a creature, having Himself created all things and having existed before anything was made.
The phrase "firstborn of the world" also cannot be considered the "first creature" of God. To expose the error of this interpretation, we can use King David as an example; he was the firstborn of his brothers (Psalm 89:27), but not the first to be born (1 Sam. 16:1-13). However, he is called "firstborn." Ephraim, the second son of Joseph (Gen. 41:52), is also called the firstborn (Jeremiah 31:9).
The phraseology "firstborn of the world" is Jewish, and as they apply it to the Supreme Being -- the Infinite, only to denote His eternal preexistence, and to identify Him as the cause of causes. It is more than evident that Paul, as a Jew raised in Jewish and Pharisaic culture and an honored sage of the Jewish people, uses this phraseology in the same way, illustrating its meaning with the following words: everything was created by Him and for Him. He is before everything, and everything subsists in Him. Thus, the interpretation that says that "He is the first creature" or included among creatures is excluded by the statements that followed when it is said of Him that "everything was created in Him, by Him and for Him," and that He is "before everything, and everything subsists in Him" (v.16-17). All these expressions clearly demonstrate that the Son is in a unique rank, outside the series of creatures.
Another rabbinic parallel, perhaps equivalent to Bekoro shel olam (firstborn of the world), is the term "Qadmono shel olam-First or Primordial of the world," used to refer to God, as did, for example, the 2nd-century Jewish sage Eleazar ben Shimeón (Bereshit Rabá 38.7 on Gn. 11:2). And also in the Zohar, where God is referred to as "Qadmono shel olam-First or Primordial of the world" (Zohar, Lech-Lecha 1.84a). It is quite likely that the apostle Paul, as a Jew immersed in his people's culture, used one of these two Jewish phraseologies in this doctrinal exposition recorded in his letter to the Judeo-Messianic community located in Colossae vv. 1:16; "Qadmono shel Olam-First-Primordial of the world" or “Bekoro shel olam–firstborn of the world." Both are words used to refer to God.
Reading Paul's key statements about Jesus, as a Jew would have done, completely immersed in his people's culture, such as when he calls Him "firstborn of the world" (bekoro shel olam-firstborn-of-the-world; or Qadmono shel olam-First-Primordial-of-the-world"), clarifies the text's message, which perfectly aligns with Jewish phraseology and ideology and with the entire content of the praise written by the apostle; “everything was created in Him, by Him and for Him,” and He is “before everything, and everything subsists in Him.” The overall idea is clear: the Messiah is above all creation. He is God.