One approach to developing faster, more accurate stereo algorithms is to seek a more complete and efficient use of information available in stereo images. The use of chromatic (color) information has been largely neglected in this regard. Motivations for using chromatic information are discussed, including strong evidence for the use of chromatic information in the human stereo correspondence process. To investigate the potential role of chromatic information in edge-based stereo algorithms, a novel chromatic matching constraint -- the chromatic gradient matching constraint -- is presented. A thorough analysis of the utility of this constraint in both the "match extraction" and "disparity selection" stages of the PMF Algorithm 1 is performed for a wide range of matching strength "support neighborhood" sizes. The performances of the algorithm with and without these constraints are directly compared in terms of disambiguation ability, matching accuracy and algorithm speed. The results demonstrate that the use of chromatic information can greatly reduce matching ambiguity, resulting in increased matching accuracy and algorithm speed.