Using the methodology called epiconography, this study examines the use and meaning of colors in Roman mosaics executed during the-kvelfth-century Church Reform. The analysis discovers the rhetorical arrangement of visual speech in the mosaics of San Clemente and Santa Maria in Trastevere. Taken from techniques of manuscript preparation, colors served in the mosaics to articulate and add emphasis to the visual narrative. Considering images and inscriptions together, the observer could "read" the mosaics and discern their meanings. This dual process enabled the mosaics' patrons and promoters belonging-to the Reformed Church hierarchy to supervise the artistic program with particular attention to visual messages