Do the forgoing comments require that the red letters be more important than the black ones? If they are all inspired, they should all coincide. Most of what Christ taught as is recorded for us, was before the sacrifice that He made, the rest comes afterward, in definition of His work of redemption.
While Paul is certainly more "theological" in his presentation, is he less inspired? Perhaps he was only 80% inspired, while Christ was 100% inspired? This seems to be the outworking of the lines of reasoning that you all are suggesting, a carving up of the NT with a pen knife.
As I recall, the early Anabaptists used all of the NT to define their faith. The concept of body dynamics is found in Paul, more completely defined than in the gospels (ie, community of goods, etc). Can we have one without the other? How would you know how the early church practiced except for the book of Acts? Can you separate Acts from Luke?
I don't find a principle in the NT writers that elevates the gospels above the rest, it seems to be an invention, though perhaps well intended, but an invention of humans, non the less. Remember, the gospels themselves are the observations of humans, and not the writings of Jesus, just like the rest of the NT. IF one part is inspired by the Holy Spirit, then all of it is, and bears the same stamp of authority and approval of YHWH.
The fact is that most of what Christ taught is eschatalogical, and how many of us ignore the real implications of that, and either ignore it, or try to explain it away as being irrelevant or unfulfilled? Why indeed should it be so hard to understand why so much more of His teachings are handled in similar fashion? We hold to the traditions of man contrary to the teachings of Jesus, but will major on some favorite passages. Let's put them together, and allow all of them to speak to us cohesively.
The principle of being "red letter focused" is not, as far as I follow it, a question of having one part of Scripture being "more inspired" than others, but recognizing that Scripture as a whole is not consistent, nor can we take all of it's commands and princples to be of equal weight. As Jesus pointed out, sometimes keeping the Sabbath holy isn't consistant with having mercy on the needy and we have to make choices. And we have to make decisions about the law of having a rail on our roof. And we have to make a determination as to whether we will listen to James' or Paul's understanding of how faith and works connect.
The "red letter" approach is to say that we begin our interpretation of the whole inspired Scripture with Jesus to help us understand what God really wants from us. Jesus not only is our Saviour and God, but He is also our Teacher, and the Scripture can only be truly understood through Him. He teaches us not only the fulfillment of the Law, and the meaning of the Prophets, but He also teaches us how to understand Paul and the significace of Hebrews. In my understanding, the OT is the text that Jesus uses to expound His principles, but they have no coherance apart from His teaching. The NT is the act of Jesus followers attempting to apply Jesus to their lives. But Jesus' teaching and life is the center of our existance. If we have nothing other than Jesus' words, then we have enough. Because we have more than just Jesus words, but also the books on which he expounded and the commentaries on his teaching, then we are richly blessed with great knowledge.
However, if we put our limited interpretation of Paul above Jesus (as some do when they say that Paul's teaching allows us to ignore the principles of the Sermon on the Mount), then we are putting Paul, not Jesus as our Teacher (even though they rightly never disagree with each other). If we place Moses or David above Jesus (as some do when they hold the principles of the warrior to be above Jesus' teachng on loving one's enemies) then we have Moses or David as our Teacher, not Jesus.
Jesus said that we are not to call each other Teacher, for only ONE would be our teacher, the Messiah (Matthew 23). So if Jesus is our Messiah, then He alone is our teacher, and Paul and James and John and Moses and David and Solomon and Isaiah etc, are only helpful as teachers if they point us to the teaching of Jesus. Sure, they can give us some good help that Jesus didn't actually say, but it is Jesus who is our doctrine.