Color yellow, or gold, speaks of life refinement and that of perfection.
[1 Corinthians 12:28-29] And God has appointed in the church, first apostles, second prophets, third teachers, then miracles, then gifts of healings, helps, administrations, various kinds of tongues.  All are not apostles, are they? All are not prophets, are they? All are not teachers, are they? All are not workers of miracles, are they?
Apollos was a teacher: [Acts 18:24-26] Now a Jew named Apollos, an Alexandrian by birth, an eloquent man, came to Ephesus; and he was mighty in the Scriptures.  This man had been instructed in the way of the Lord; and being fervent in spirit, he was speaking and teaching accurately the things concerning Jesus, being acquainted only with the baptism of John;  and he began to speak out boldly in the synagogue.
In Ephesians 4:11-14 we read about five types of ministries, which bring maturity (Greek TELEIOS, perfection). Perfection is a much avoided word, yet it is the same word Jesus used in Matthew 5:48, "Therefore you are to be perfect, as your heavenly Father is perfect." God does not attain to perfection for He is perfect, but since we are God's extensions we conclude that He brought us to earth in order to be perfected just as He is perfect. The seed that fell to the ground from a fruitful tree produces another tree with same fruits. After we ATTAIN, we will eat of the Tree of Life and like Enoch of old we also would be translated. Therefore, the Tree of Life, from which we were prevented to eat, still stand in its place; once we attain perhaps then we shall be perfect and be allowed to eat of the Tree? Perfection is not of our own doing but of God's. For this reason God gave us the ministry of the Holy Spirit (John 16:13) to lead us and guide us into all the truth. In John 8:31-32 we read about five steps to freedom and a complete release from any bondage, especially religious one.
First step is to believe. The second is to continue in that faith. Third is to become a disciple of the same. Fourth brings the knowledge of truth. The fifth brings total freedom. This can be synchronized with Ephesians 4:11-14. (...) until we all attain to the unity of the faith, and of the knowledge of the Son of God, to a mature man, to the measure of the stature which belongs to the fullness of Christ.  As a result, we are no longer to be children, tossed here and there by waves and carried about by every wind of doctrine, by the trickery of men, by craftiness in deceitful scheming.