How do Jehovah's Witnesses reconcile John 1:3 with Colossians 1:15-16?

Interesting questions here, Mike. I suppose it would be beneficial to tackle them in reverse order since no. 2 should be a slightly more simple answer.

2. Should we expect to see a future revision to the NWT translation of John 1:3 so that it reads:

All other things came into existence through him,+ and apart from him not even one other thing came into existence.

My "answer": It's difficult to know. Over the years the translation teams have remained anonymous (although there has always been plenty of speculation as to the identity of the team members). You are likely aware that there have been multiple revisions since the original, and the revision previous to the current one rendered Colossians 1:16 as follows (notice the brackets):

because by means of him all [other]* things were created in the heavens and upon the earth, the things visible and the things invisible, no matter whether they are thrones or lordships or governments or authorities. All [other] things have been created through him and for him.

Here's a thought taken from the introduction to that edition regarding the use of such brackets:

Single brackets [ ] enclose words inserted to complete the sense in the English text.

These brackets are found all over the translation and, in my opinion, are a nice feature to have. Consider John 1:1a in said revision:

In [the] beginning the Word* was

It's useful to know that the word "the" has been added for readability and comprehension in English. It's not very correct or senseful to say, "In beginning was the Word" in English even though that's what the original Greek says. The problem comes when the addition of the bracketed word has theological implications and that appears to be what we're dealing with here. I assume that their basis for adding "[other]" in Colossians 1 would be equally applicable in John 1 unless I'm missing something. John 1 is using a different verb than Colossians 1 and John 1 is also one of the most famous passages of the NT...so maybe that has something to do with the difference? It's also framed a bit differently in John vs. Colossians. For example, John is speaking of the beginning alluding to Genesis 1 and mentioning that the Logos was already there. However, Colossians speaks of Christ as the beginning (1:18) so they are perhaps referencing different beginnings. A final morsel for thought here also is that John 1 opens by speaking about the Logos, not Christ, which is something that Biblical Unitarians are fond of pointing out. Even Christian scholar James Dunn points out the following:

To be somewhat pedantic, according to the Johannine prologue, Jesus is not the Word; he is the Word become flesh.

(Did the first Christians worship Jesus? page 127). - BTW I recommend this book...

So this could account for some translation differences between John and Colossians as well.

Now on to no. 1:

How do Jehovah's Witnesses reconcile John and Colossians?

I'll assume you are speaking here about a reconciliation between John 1 and Colossians 1 in the NWT because there wouldn't be anything to reconcile if one were using another translation like KJV or ASV, for example. These translations and others are both available on their site.

So, the essential question as I understand it is as follows: "How can one say Jesus is a created being if John 1:3 says that all 'created' things came to be through Him but Colossians 1:16 states that all 'other' created things came through Him"?

The simple answer is that he was created in a very different and unique way: directly by the Father. I don't know if anything is written about that production in their publications as far as whether it was "out of nothing" (think Arius) or "from the same substance" (think Nicaea and the "begotten" not "made" argument). I think there's a good reason for that, though: they don't have centuries of ecumenical councils convened by some of the sharpest theological and philosophical minds our world has known (like mainstream Christianity). In fact, I found this statement from a Watchtower most interesting:

First, it must be stated that Jehovah’s Witnesses do not have a particular “Christology,” defined as “the theological interpretation of the person and work of Christ.” They share the view of the Christian layman who is recorded as having bluntly told the wrangling theologians assembled in Nicaea in 325 C.E.: ‘Christ did not teach us dialectics, art, or vain subtleties, but simple-mindedness, which is preserved by faith and good works.’ Apparently this man had suffered for his faith in Christ, even as many of Jehovah’s Witnesses have. Like him, they have no faith in theological philosophy. They accept with simplicity what the Bible states about God, Christ and the holy spirit, and they are willing to suffer for their simple faith and prove it by good works.

Source: Watchtower, Sept. 1, 1984

Now, back to whether or not Jesus was made "out of nothing" or begotten "of the same substance" of the Father, I found the following that suggests it was the latter:

Like a word that is produced by a speaker, the Word or Logos is God’s creation, God’s first creation.

Source: Watchtower, Oct. 1, 1961

This seems to be in line with at least a couple of Church Fathers that I can think of, although I know they can be quoted to appear to support either side of the centuries-long debate.

One other interesting musing that I think would apply here has to do with our modern understanding of the dimension of time. I suppose this is sort of a personal view that I hold so I can remove if needed. Time as we know it today is linked to the physical universe. If you can exist outside of the universe you can exist outside of time from our point of view. This being the case, if the Son was begotten before the creation of the universe, then He is indeed eternal from our human point of view. He wouldn't be eternal from the Father's point of view, though. I suppose you wouldn't want to push the point too far though because that would place even created angels in the eternal realm from a human point of view (but they wouldn't be eternal from the Father and Son's point of view). Just something interesting that I think about often...maybe more than I should. :)

At second glance the clarifying text under the question seems to be the type that falls in the category of deserving a reaction with a counter question (similarly as Jesus in Matthew 21:23-27):

How do bible translators reconcile Psalm 83:18 where the name of God is typically rendered, with the over 6800 other bible verses where the name of God originally appeared as the tetragrammaton YHWH, or Jehovah was carefully removed and replaced with LORD?

But it is more beneficial to apply Hanlon’s razor, even if just for the sake of giving the proper etiquette example to the LLMs trained with our answer data to become assertive informative helpers.

Focusing on: “How do Jehovah's Witnesses reconcile John 1:3 with Colossians 1:15-16?”

In a non-trinitarian perspective such as JW's, Jesus is seen as God’s Son, in the sense of his first direct creation (Proverbs 8:22-23), his only direct creation by means of which all other things are created (John 1:3), and Jesus is considered to have a pre-human existence (John 8:58) and subordinate to God (Philippians 2:-7). This perspective is maybe best summarized in 1 Corinthians 8-6. From this perspective the many renderings and translations of John 1:3

All things came into existence through him, and apart from him not even one thing came into existence. [NWT]

Through him all things were made; without him, nothing was made that has been made. [NIV]

God created everything through him, and nothing was created except through him. [NLT]

are quite clearly compatible, and could be considered even supportive of this aforementioned perspective, that the Son Jesus, was the instrument through whom all things were created.

From a non-trinitarian perspective, the verse in its context seems to emphasize the role of Jesus Christ in his prehuman existence in creation. John 1:3 starts with δι’ (di’) denoting the channel of an act, often translated with trough (him, then refers to Jesus in his pre-human existence). Further the preposition χωρὶς (chōris, Strong's 5565) often translated with apart from, separately from; without, makes a distinction between Jesus and the rest of Creation. From this view, the verse simply mentions Jesus as the channel of creation (see also Hebrews 1:1-2).
It is difficult to find a justification to interpret this verse in Greek or any translation, such that it would lead to the conclusion that "either Jesus brought himself into existence or he was not brought into existence".
John 1:3 is not used as a justification pillar by non-Trinitarians that Jesus was created or brought to existence by God directly, and is not equal to God, these concepts are based on for example. Revelation 3:14, Proverbs, 8:22-23, Mica 5:2 and Philippians 2:5-7.

If we consider John 1:3 besides a translation of Colossians 1:15-16 that is one the least favorable for the non-trinitarian perspective:

¹⁵ He is the image of the invisible God, the firstborn over all creation. ¹⁶ For by Him all things were created that are in heaven and that are on earth, visible and invisible, whether thrones or dominions or principalities or powers. All things were created through Him and for Him. And He is before all things, and in Him all things consist. And He is the head of the body, the church, who is the beginning, the firstborn from the dead, that in all things He may have the preeminence. [KJV]

There is still no contradiction or conflict between the essential content in John 1:3 and Colossians 1:15-16, and also not any contradiction with the non-trinitarian perspective. Even though translations differ in terms of „by Him“, „in Him“, and „through Him“, about which there are endless discussions possible. From the non-trinitarian perspective, the distinction between Jesus and the Father is also made clear by one of the following verses in the context of Colossians 1:19

For it pleased the Father that in Him all the fullness should dwell, and by Him to reconcile all things to Himself, by Him, whether things on earth or things in heaven, having made peace through the blood of His cross. [KJV]

So from a non-Trinitarian perspective, as well as the particular perspective of Jehovah's Witnesses, there is no contradiction, conflict, and no issue in reconciling the verses in John and Colossians, even without the insertions of the word “other”. Of course, other and different interpretations and perspectives are possible, an interesting overview can be found at BibleHub.

Some of the Bible commentaries there are supportive of the trinitarian view, of which there are also various variations. Some support the view of Jesus as a created Instrument, while others exclude him from the creation.

An important valid sub-point of the text in the question remains however the justification of the translators of the NWT to add the word “other” in various verses of Colossians 1, where I was not able to find any other bible translations doing so.

In the context of Colossians 1:16, you might find "τὰ" in phrases like "τὰ πάντα" (ta panta), which could be translated as "all things" or "everything." The article "τὰ" serves to make the noun "πάντα" (all, everything) specific. Does making it specific in this case justify adding other? I am not sure and would tend towards no. There are, however, other verses where the original Greek does not explicitly have a word of similar meaning to other, or requires it in the translation, but where the word other is still included in some English translations for clarity. Examples are

Acts 5:29

Peter and the other apostles replied: “We must obey God rather than human beings! [NIV]

1 Corinthians 11:21

For in eating every one taketh before other his own supper: and one is hungry, and another is drunken. [KJV]

The KJV typically renders such extra words that are included for clarity in italics where for example the NIV, does not. The NWT also did not use italics.

The NWT also adds/includes the word other in Philippians 2:9.

For this very reason, God exalted him to a superior position and kindly gave him the name that is above every other name, [NWT]

Also without including other, the context of the following verse 10, clarifies the relative position of Jesus to God the Father.

And that every tongue should confess that Jesus Christ is Lord, to the glory of God the Father. [KJV]

While from a non-trinitarian perspective, these examples can be considered small clarifications/changes/additions. I must admit that can feel empathy for Trinitarians who consider the translation of these verses in the NWT as biased. On the other hand, there are also many more examples of Bible translations with a trinitarian bias.

Comming back to John 1:3: the original Greek is unambiguous there, resultingly almost all translations are clear enough, to avoid reasonable misunderstandings based on this verse, and there seemed no need to include the word 'other'.

In my personal view, it was unnecessary to include the word other in the discussed verses in Colossians and Philippians, at least the use of italics, or brackets (such as used in the Kingdom Interlinear translation) would have been very appropriate. At this point, it might be important to mention that Jehovah’s Witnesses do not have to consider the NWT, or any other content of the Watchtower Bible and Tract Society as infallible. In fact, the humility that the Governing Body admits themselves not to be inspired, or perfect, is what separates them from many other Christian religions and dominations. It is one of the few religions that even keep lists with changes in understanding, instead of covering them up. So personally, I have some hope that maybe in a future revised translation, these inclusions of “other” will be omitted, rendered in italics, or satisfactorily explained.

John 1:3 says this about the Word, who was with God in the beginning:

All things were made by him; and without him was not any thing made that was made. (KJV)

Through him all things were made; without him nothing was made that has been made. (NIV)

All things came into existence through him, and apart from him not even one thing came into existence (NWT)

Here is the official Jehovah's Witness explanation for why the New World Translation added the word "other" in Colossians 1:15-16 (taken from The Watchtower—1970 April 15 page 255 – Questions from Readers):

Bible writers often took for granted that certain things would be understood, just as writers in our day do. For example, the apostle Paul states, as we read at Colossians 1:16, that by means of Jesus Christ all things were created in the heavens and on earth. But since we know from Revelation 3:14 that Jesus himself was also created, the New World Translation adds the word “other,” which clearly is what the apostle had in mind. But even here, it might be added, that, were it not for the prevalence of the trinitarian teaching that Jesus was not created, it would not have been necessary to add the word “other.”

Both the addition of "apart from him" in John 1:3 and "other" in Colossians 1:15-16 were added in the NWT in opposition to Trinitarian understanding that the Word was never created but existed (along with the Holy Spirit) from eternity.

That is how they reconcile those two passages of Scripture.

On the JW official website, I did a search for John 1:3 and found many occurrences, including these:

“This firstborn spirit Son was used by his Father in the creation of all other things. (Joh 1:3; Col 1:16, 17)” giving the reference as the ‘Insight’ Vol. 2 book, pp.52-57. I looked it up in my copy but found absolutely nothing on John 1:3.

Also given: “John points out that this One was with God “in the beginning” and that “all things came into existence through him.” (Joh 1:1-3)” reference ‘Insight’ Vol. 2 pp.91-94. Those pages deal with John’s Gospel account. Page 94 has those exact words (above) and nothing else in the 4 pages relevant to the OPs question.

Another reference for John 1:3 was from that same volume, pp. 1200-1203 (under ‘The Word’): “When he was in the beginning with God all things were created through him; without him came no created thing into being.” (Joh 1:1-3) ... All things came into existence through him, and apart from him not even one thing came into existence.”—Joh 1:2, 3.” Those Bible quotes are on page 1203, the first being from ‘A New Translation’ by Professor Charles Cutler Torrey. Although Col. 1:15,16 is cited after the second Bible quote (from the NWT), not a word of explanation is given as to any connection, or anything about ‘other’ being added in Colossians, but not added in John 1:3.

This reference sounded hopeful – “According to Colossians 1:15, 16 and John 1:1-3, by means of whom were all other things created by God?” reference, the 'Holy Spirit' book pp. 16-34. I looked out my copy and found that question on page 27, linked to paragraph 24. I begin my quote from halfway through paragraph 23:

23 …“He is the image of the invisible God, the firstborn of all creation.” (Colossians 1:15) So, after God created “the firstborn of all creation,” all things that were brought into existence afterwards were other creations. When creating all those other things, God took into his employ his “only-begotten Son.”

24 In bearing out this thought, the apostle Paul first mentions the “firstborn of all creation” and then goes on to say: “Because by means of him all other things were created in the heavens and upon the earth, the things visible and the things invisible.” (Colossians 1:16) Now we can understand the apostle John’s words in John 1:1-3:… [and quotes the NWT of those three verses, which has no addition of the word ‘other’.] HOLY SPIRIT – The Force Behind the Coming New Order! pp.27-28, published 1976

There was nothing there, or elsewhere, relevant to the question asked by the OP.

However, an entire 64 page booklet called “The Word” Who is He? According to John” (published 1962) was mainly devoted to expounding John’s Gospel, so I went through my copy of it. It wasn’t until p.59 that there was any mention of John 1:3, which gave the NWT rendition, commenting: “Certainly the Word or Logos, whom God his Father used in bringing into existence all other creatures, was the chief or the firstborn among all the other angels whom the Hebrew Scriptures call elohim or “gods.” And that was it: not a word relevant to the question asked by the OP.

Conclusion - Having spent many hours searching many references given on the official website, and coming up with nothing relevant to the OPs question, all I can say by way of an answer is that there seems to be no attempt to explain why the NWT does not add ‘other’ to John 1:3 whilst adding it five times in Colossians 1:15-17. This silence is actually very interesting.

Of note is that this Watchtower article said of Col.1:16

…Paul states, as we read at Colossians 1:16 that by means of Jesus Christ all things were created in the heavens and on earth. But since we know from Revelation 3:14 that Jesus himself was also created, the New World Translation adds the word “other,” which clearly is what the apostle had in mind. But even here, it might be added, that, were it not for the prevalence of the trinitarian teaching that Jesus was not created, it would not have been necessary to add the word “other.” [bold emphasis mine] Paragraph 4 of Questions From Readers

This makes it all the more intriguing as to why the Watchtower Society has not added the word ‘other’ into John 1:3 which is totally trinitarian.