Iconography
Iconography is literally the writing of icons. The term is also used to refer to the reading or study of icons.The word iconography is also used to refer to the archetypical images, scenes and characters used in symbolic representation, such as the Tarot. For example, in films of the "Western" genre, such tropes as "cattle drive", "saloon", "gunfight", "gunfighter" and "sheriff" constantly recur.
In art history, iconology is the study of the conventional meanings of works of art that are meant to convey some doctrine or traditional story. For example, through iconology, the saints represented on cathedral windows can be identified by noting the tools or animals that were included in the pictures specifically for the sake of identification.
In Eastern Orthodoxy, the church has established an extensive set of rules and guidelines to be used for writing icons, both in general and for particular icons. (Note on word usage: icons are not "painted", they are "written." They are also "read" by the viewer, rather than just viewed.) Because the icons communicate theological truth, they are often just as careful to write icons correctly as they would be to compose written doctrines and dogmas. Eastern Orthodox theologians often find it useful to "quote from" or refer to a particular icon when making a point, just as they might cite a document written by an earlier theologian or council. The responsibility of writing icons is often carried out by monks. A saint must be canonized by a synod of bishops before icons of the saint can be written and put into use and venerated.
A nimbus of light is often shown around the heads of those who believe in God, to symbolically show that they are illumined by the Light of Jesus Christ. Occasionally, this is used to make pointed distinctions, as in some icons of the Crucifixion of Jesus Christ that show a nimbus around the crucified thief who believed in Jesus, but not around the crucified thief who cursed him instead.
Jesus and the saints are almost never shown smiling, frowning or angry, but are intended to appear passionless and sober. This appearance is often mistaken for sadness, but it is intended to show their seriousness, and their freedom from the vicissitudes of emotion.
In Byzantine, Greek and Russian icons of Jesus and Mary, the color red represents divinity, while the color blue represents humanity. Accordingly, Mary is shown wearing something blue, covered with a red outer garment, to show that her humanity was "overshadowed by the Holy Spirit", i.e. God. On the contrary, Jesus is shown wearing something red, covered by a blue outer garment, to show that he was God who "put on" human flesh.
Symbolism in icons
The background in icons is often gold colored, or some kind of gold leaf. This most often represents the radiance of Heaven. If it is intended to depict a scene on Earth rather than Heaven, some buildings or mountains will be included to indicate this.