This paper seeks to clarify the assertion that the urban built environment can be understood as arising from the process of human communication. To accomplish this task a study of color in public spaces is introduced. The results of statistical analyses derived from photographic images of a systematic sample of seven hundred building facades are reported. They reveal strong relations between organizational function, and price level, and the facade's pattern of color. Explanation of these findings stresses (I) the value of material expression--the integration of physical artifacts in interaction--as a generally overlooked aspect of communication and (2) the relation of color--as one facet of this material expression--to its complements, including architectural style, physical size, and building materials.