Understanding the characteristics of the stimulus values of colors obtained by subtractive color mixture is not easy, compared with those obtained by additive color mixture, since the relationship between superimposed absorption media and the stimulus values is not simple. In this article, using the assumption of the Lambert-Beer model for subtractive color mixture, we prove several theorems regarding the stimulus values of colors obtained by subtractive color mixture. Although these theorems are proved theoretically, numerical illustrations are also shown to confirm the theorems. The results of this paper will contribute to a systematization of subtractive color mixture. (C) 2003 Wiley Periodicals, Inc.