John 1:18

For the law was given through Moses, but
God’s unfailing love and faithfulness came through Jesus Christ. No one has ever seen God. But the unique One, who is himself God, is near to the Father’s heart. He has revealed God to us.

-- John 1:17-18 (NLT)

Some modern translations say that Jesus is the God who reveal "unfailing love and faithfulness" where the "law" of Moses only reveal condemnation, while other translations read:

For the law was given by Moses, but
grace and truth came by Jesus Christ.
No man hath seen God at any time;
the only begotten Son, which is in the bosom of the Father, he hath declared Him.

-- John 1:17-18 (KJV)

In other words, some know about God only by the law (teachings) of Moses. By those teachings alone, "No man hath seen God". However, by "grace and truth" which come by Jesus Christ (His son), who "declare" who the Father is, the disciples got to know God.

Colossians 1:15

He is the image of the invisible God... -- Colossians 1:15 (ESV)

If one thing is "the image" of another thing, it means "the image" is not the original. In this case it proof Jesus is not God Himself.

However, some would argue that Jesus was God "body" (puppet, avatar or extension) on earth.

Fortunately, Paul explains in another letter:

But we all, with open face beholding as in a glass the glory of the Lord, are changed into the same image from glory to glory, even as by the Spirit of the Lord. -- 2 Corinthians 3:18 (KJV)

This means we are too being changed into the image of God, without reincarnating into gods ourselves. Paul meant that we should represent God like Jesus did. For example:

For a man ought not to cover his head, since he is the image and glory of God. -- 1 Corinthians 11:7 (ESV)

The Book of Genesis explains that this is why God created humans:

So God created humankind in His own image. In the image of God he created him. -- Genesis 1:27 (ESV)

Therefore, being the "image of God", simply means that the "invisible God" choose to represent Himself to his creation through humans. That is why it is so important not to present a distorted image of God, but to follow the example of Jesus.

Titus 2:13

For the grace of God that brings salvation has appeared to all men, teaching us that, denying ungodliness and wordly lusts, we should live soberly, righteously, and godly in the present age, looking for the blessed hope and glorious appearing of our great God and Saviour Jesus Christ, who gave Himself for us, that He might redeem us from every lawless deed and purify for Himself His own special people, zealous for good works, zealous for good works. -- Titus 2:11-14 (NKJV)

Out of context it seems like Paul is saying "our great God who is also our Saviour Jesus Christ", but the scripture was influenced by the translator's interpretation. The direct Interlinear translation from BibleHub is:

... awaiting the blessed hope and the appearing of the glory of the great God and Saviour of us, Christ Jesus...

Other scholars translate the same scripture as such:

For the grace of God has appeared, bringing salvation for all people, training us to renounce ungodliness and worldly passions, and to live self-controlled, upright, and godly lives in the present age, waiting for our blessed hope the appearing of the glory of our great God and (or namely)

Savior Jesus Christ who gave himself for us to redeem us from all lawlessness

and to purify for Himself a people for His own possession who are zealous for good works. -- Titus 2:11-14 (ESV)

This version could be interpreted that Jesus Christ is God's glory and not that Jesus is God Himself.

If Paul intended to lead Titus to belief Jesus is God, he would have said so in the opening of his letter to Titus, but instead he writes:

Paul,

• a bondservant of God and
• an apostle of Jesus Christ,

according to the faith of God’s elect and the acknowledgment of the truth which accords with godliness, in hope of eternal life which God, who cannot lie, promised before time began, but has in due time manifested His word through preaching, which was committed to me according to the commandment of God our Savior;

To Titus, a true son in our common faith:

Grace, mercy, and peace from

• God the Father and
• the Lord Jesus Christ our Savior.

-- Titus 1:1-4 (NKJV)

Paul clearly states that "God" and "Jesus Christ" is two different persons and that he has a different relationships with each one.