The existing literature on color psychology has focused on the cognitive and perceptual processes of colors. However, few researchers have explored the potential role of colors in shaping people’s environmental decision-making and behavior, a crucial issue related to sustainable development. Indeed, recent research has documented the salient effects of colors on consumers’ decision-making and purchasing behavior. Drawing upon the self-expansion theory, this study aims to investigate an interactive effect of people’s color green preference and their nature exposure experiences on sustainable consumption behavior, as well as the mediating mechanism of nature-connectedness. By conducting a survey study (N = 400), we found evidence of a significant interactive effect of color-green preference and nature exposure experiences on nature connectedness, which, in turn, promoted sustainable consumption behavior. This study extends research in color psychology by exploring how people’s preference for green colors could shape their sustainable consumption behavior. Also, it contributes to the literature on environmental behavior by understanding a self-expansion process of when and why green-preferred individuals consume in an environment-friendly manner.