Petr Pokorny also documents what he calls "the accumulation of prepositions" (an apparent Hellenistic device) and observes that the writer of Colossians uses this technique in order to show that God is the Creator, but Jesus Christ "represents" God's creation:
"Since God the Father is the initiator of creation, the preposition 'from' is not used here. Otherwise it is difficult to distinguish the functions of the various prepositions from one another. They, as a whole, are to have a cumulative effect. 'In' (instrumental ἐν) and 'through' mean almost the same thing; only the phrase 'for him' is capable of pointing to the eschatological goal of creation (Cf Rom 11:36)."
Quoted from Pokorny, Petr. Colossians: A Commentary. Peabody, 1991, pp. 78-79.
While some might look to Romans 11:36 as a proof-text which demonstrates ἐκ being applied to the "triune" God, the application of ἐκ to the Father only with respect to creation indicates that this Greek preposition is not being applied to the Son in 11:36.
From Robertson's Word Pictures in the NT:
Of him (ex autou), through him (di autou), unto him (ei auton). By these three prepositions Paul ascribes the universe (ta panta) with all the phenomena concerning creation, redemption, providence to God as the Source (ex), the Agent (di), the Goal (ei). For ever (ei tou aiwna). "For the ages." Alford terms this doxology in verses Romans 33-36 "the sublimest apostrophe existing even in the pages of inspiration itself."
Another quote that has a bearing on our understanding of Colossians 1:15-17 is taken from Emil Brunner's Dogmatics (Volume I:308):
"In this connexion the truth which we have already seen acquires new significance, that the world, it is true, was created THROUGH--διά--the Son, but not BY--ὑπό--the Son, that it has been created IN Him and UNTO Him, but that He Himself is never called the Creator. It has pleased God the Creator to create the world in the Son, through the Son, and unto the Son. The fact that between the Creator and the Creation there stands the Mediator of creation means that the world is an act of the freedom of God, that it does not proceed from the Logos."
While Brunner thinks that the Son of God is "eternal," he does not believe that the Son is ever called Creator in Scripture: the Logos is the mediate agent of creation and the one through whom God brings forth the KOSMOS. But the Son is never called Creator in Scripture. Not only does the apostle Paul describe the role of the LOGOS in passive verbal terms at Col 1:15-17, but the envoy of Christ who penned Colossians missive refuses to employ ὑπό (hUPO) to delineate the role of the LOGOS vis-à-vis creation.
Brunner insists hUPO shows us that Christ is not being identified as the Creator by the apostle in Colossians 1:15-17, and I would submit that researching Greek literature will support his point. If Paul had wanted to call Jesus the Creator in Colossians, he could and likely would have used hUPO instead of διά or ἐν.