The color composition in modern architecture has been often characterized in a simplistic manner. In fact, this is a complex phenomenon to be studied because of the disparity of proposals and the uniqueness of the architects involved. This research starts with a comparative study of three of the most relevant color composition systems in the first half of the 20th century (Purism and Le Corbusier, Expressionism and Taut, Neoplasticism and Rietveld), and aims to find common characteristics among them, discussing the validity of some widespread ideas about it, such as the prominence of white hues, the use of flat colors, or the conception of color during the ideation phase. We propose and demonstrate three principles that are not categorical about the color composition in modern architecture: it limits the variety of hues; it not only uses white color but also displays color to conform shapes and to transform them; color has ethical connotations and not only aesthetic ones. (c) 2011 Wiley Periodicals, Inc. Col Res Appl, 2012; Published online 1 March 2011 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/col.20657