Not a frivolous question at all, TW. Traditionally, as you point out, Icons were written using egg tempera and were written directly on solid wooden boards. Icons adorning church walls were sometimes frescoes and sometimes, as at Hagia Sophia in Constantinople, they were mosaics. Materials used today depend on the jurisdiction and the location. Egg tempera is still used by very strict traditionalists in Eastern Europe but a great many Iconographers now use acrylic paints and write Icons on manufactured boards. These materials are more consistant, more dimensionally stable and are thought to extend the life of the Icon. Large Icons intended for application directly to church walls are now usually written on artists' canvas in a studio then taken to the site and applied to the wall.

In the Orthodox Church the term for the Mother of Jesus is Theotokos, a Greek word meaning Mother of God. The colors are traditionally those shown in this example. In Byzantine Iconography, the Theotokos is never depicted wearing ultramarine blue although she is sometimes shown wearing a blue gown under her maroon robe. The three stars you see in the example symbolize her virginity before, during and after carrying the Creator in her womb.

The same site I linked above also presents a wonderful step-by-step explanation of the techniques used in writing an Icon, just click through the steps. If you snoop around the site, there are also examples of many traditional Icons.

      - Mark