The First Sunday of Great Lent in the Orthodox Church commemorates the 7th Ecumenical Council, held in 787 in the city of Nicea, and its decision that iconography is theology in lines and colors which affirms the incarnation in a unique and essential way.
“The key theological teaching defended by the Second Council of Nicaea is that as Christ is the image of the invisible God (Col. 1:15), we are able to depict him in colors; that iconography is a theological statement, an affirmation of our faith. This has two further important consequences. First, that we do not look elsewhere to try to see or understand who and what God is: in Christ, the fullness of divinity dwells bodily (Col. 2:9) – the fullness; we do not find God elsewhere, by some other means. Second, the holy icons are not simply religious art. We don’t place them in our churches and house simply for decoration. While reflecting different artistic schools, icons are properly a theological statement, reflecting the transformative power of God at work in Christ: the light who shines in darkness, illuminating the darkness; the one who shows that the form of a servant is in fact the lordly form; the one who by his death destroys death.
The icons are a witness to this and continue to communicate this transformation for those who have eyes to see. As the apostles depicted Christ in words, we also depict him in colors, including all the aspects of his work and salvation, all the various events we celebrate. We also depict all those who have put on Christ, all those in whose lives, words, and deeds we can see the Spirit of Christ breathing – the Theotokos and all the prophets, apostles, martyrs and saints of every age. We do not treat the icons as magic idols or ethnic art, and we certainly do not worship creation rather than the Creator; but venerating the icons, we pay honor to the ones depicted on them, and so worship the one God. Such is the historical reason for celebrating this Sunday as the Sunday of Orthodoxy.” (John Behr, The Cross Stands While the World Turns, pp 27-28)
Great Lent was and is also a season of preparing catechumens for baptism. Thus there is a strong catechetical emphasis in the themes and scripture lessons throughout Great Lent. That Jesus is Mesiah, Lord and Savior, God incarnate, becomes central to the Lenten proclamation of the Gospel.