Human kansei is one of the important factors in recent product development. Thus, management of knowledge about consumers' feelings is an essential task in current industrial design. For the purpose of such the knowledge management, development of a descriptive method to identify feelings is needed. In this paper, we measured implicit attitudes to color combinations using affect misattribution procedure, and we analyzed proportions of positive responses to each stimulus. The results showed that chroma contrast was explained by a concept of perceptual fluency. According to the finding, we discuss significance of the perceptual fluency which links physical features and impressions from the viewpoint of ontological description. The discussion indicated a need for development of a descriptive method for correspondence between physical features and impressions explained by perceptual fluency (e.g. symmetry, contrast, prototypicality).