Colossians 1:15
"He is the image of the invisible God, the firstborn of all creation." ESV. My emphasis.
Matthew 18:10
"See that you do not despise one of these little ones. For I tell you that in heaven their angels always see the face of my Father who is in heaven."
Since "which we have seen with our eyes" 1 John 1:1 applies to Jesus, therefore "the invisible God" that Jesus images would appear to be the Father. If so, how can the Father be "invisible" when His face is always seen by angels?
The Bible is the product of human and divine efforts, 2 Peter 1:19-21 -
We also have the word of the prophets as confirmed beyond doubt. And you will do well to pay attention to it, as to a lamp shining in a dark place, until the day dawns and the morning star rises in your hearts. Above all, you must understand that no prophecy of Scripture comes from one’s own interpretation. For no such prophecy was ever brought forth by the will of man, but men spoke from God as they were carried along by the Holy Spirit.
Therefore, among other things, the Bible is written from the observer ability of a human. The fact that God is invisible (Col 1:15), simply means He is invisible to humans.
God, angels and demons are all spirit beings, clearly very different from humans - see appendix below.
Thus, the fact that God is invisible to humans (Col 1:15, 1 Tim 1:17, Heb 1:3, 11:27, 1 John 4:20) but quite visible to angels/spirits (Matt 18:10) causes no contradiction whatever.
As if to confirm this conclusion, when in the next life we get new "heavenly bodies" (1 Cor 15:35-50), we will be able to see the face of God as well:
They [the redeemed] will see His face, and His name will be on their foreheads.
APPENDIX - Spirit Beings
