Paul says at Col 1.15 that Jesus Christ, the Son of God, is the image of the invisible God, the firstborn of all creation. You might think, initially, that this kind of language ascribes mere creaturely status to Jesus, as if he weren't also the Logos of God incarnate. Thinking thus you would be mistaken, however.
The fourth century Nicene theologians had a helpful rule about understanding language such as this: whatever ascribes creaturely qualities to Jesus is to be understood in reference to his humanity. Athanasius says in Expositio fidei 4: Each text then which refers to the creature is written with reference to Jesus in a bodily sense, that is, as referring to Jesus' assumed humanity. Likewise Gregory of Nazianzus says, Whatever we find joined with a cause we are to refer to the Manhood, but all that is absolute and unoriginate we are to reckon to the account of His Godhead (Or. 30.2).
Applying this principle to the text cited from Colossians, therefore, we find that Paul is making an affirmation about Christ incarnate: he is the image (εἰκών) of God, as mankind was called to be in Genesis (cf. Gen 1.26-7 LXX). In other words, the idea is that whereas Adam failed to embody the character and nature of God as a kind of living icon in the garden by embodying that selfless and disinterested love from which God created, Jesus on the other hand did do this, precisely by dying for the sins of the whole creation to reconcile it to God (vv. 19ff.). By doing so he restored the image of God in mankind.
And we read that Christ is the firstborn of all creation, not because he was the first thing created, as the Arians would have understood. Rather this is a reference to the exalted stature of Christ's human nature: truly it has taken dominion over the entire world, through its resurrection and ascension to the right hand of God. Once again, Genesis affirms that God had created humankind to embody the rule of God over the world, but humanity had failed in this respect. But Christ says after his resurrection that, All authority in heaven and on earth has been given to me (Mt 28.18). And Paul says elsewhere that, And being found in appearance as a man, he humbled himself by becoming obedient to death—even death on a cross! Therefore God exalted him to the highest place and gave him the name that is above every name (Phil 2.8-9).
Now how could Christ have accomplished these things if he were not God? How could he have divinized and deified and sanctified his human nature, and restored to it the image and likeness of God, if he weren't himself the divine Logos by which all things had been created? The starting point for ordinary human persons is not one of moral neutrality and infinite potential in either direction, either towards godliness or godlessness. Rather the starting point for humanity is death in sin and trespass (cf. Eph 2.1ff.). Because Christ was able to do all these things, consequently he is not merely man but also God himself. As the Nicene fathers stressed again and again, only God can save.