Christians and non-Christians sometimes quote Jesus' words in the Bible as though they have more authority than the rest of the Bible. People might dismiss something taught by Paul or Moses by saying, "Well, Jesus never said anything about..." and fill in their specific topic. Some Bible versions have Jesus' words printed in red, leaving the rest of the text in black. Some have developed the mistaken notion that the "red letters" are more authoritative than the black letters, that we should pay more heed to quotations from Jesus' ministry than what is taught elsewhere in the Bible.
This is an incorrect understanding of the Bible, though. And it's especially troubling when Christians take this approach because it's not the orthodox, historic Christian view. All of the words of the Bible were God-breathed, inspired by God, and have equal authority. Jesus, as part of the Trinity, then is speaking from Genesis 1 through Revelation.
Peter expresses this in 2 Peter 1:21: "For no prophecy was ever produced by the will of man, but men spoke from God las they were carried along by the Holy Spirit."
Wayne Grudem explains in his book Systematic Theology,
Thus God's words spoken through human lips [or pen] were considered to be just as authoritative and just as true as God's words of personal address. There was no disminishing of the authority of these words when they were spoken thorugh human lips. To disbelieve or disobey any of them was to disbelieve or disobey God Himself." (p. 100)
An example of this is in Act 4:25-26 where Peter and John, praising God after having been released from the Sadducees said,
[Sovereign God], through the mouth of our father David, your servant, said by the Holy Spirit,
“‘Why did the Gentiles rage,
and the peoples plot in vain?
The kings of the earth set themselves,
and sthe rulers were gathered together,
against the Lord and against his Anointed
They credited David's words recorded in the Psalm 2 as having been God's own words through the Holy Spirit. This is the Christian view of the entire Bible.
As Christians, we cannot focus primiarily on the red letters. The whole Word of God is our teacher and guide. If you want red letters, make them all red because they're all from Jesus.