“Two-Worlds in Old Russian Icon Painting” from Icons: Theology in Color by Eugene Trubetskoi.
To conclude this discussion, it remains to be said that the icon painters were also fully aware of the most beautiful of all the manifestations of solar light, the rainbow. I have mentioned…that in the Novgorod icons of the Virgin the creatures united around her in Christ form a many hued rainbow. A remarkable treatment of this rainbow, showing deep insight into its mystical essence, can be found in the icons “The Virgin of the Burning Bush…” Here a single ray of God’s sun is refracted into a multicolored hierarchy of angels gathered around the Virgin and ruling the earthly elements through her. In this aura every spirit has its own distinct color; but the single ray associated with the Mother of God, the flame that shines through her, unites in her the entire spiritual range of the heavenly spectrum: the entire many-colored angelic and human world burns with that flame. Thus the Burning Bush stands for the ideal of the “enlightened,” glorified creatures—a world that has come to embrace the Divine Word and burns in its fire without being consumed.