Opponent-process theory is a psychological and physiological model that explains how emotions are regulated. According to this theory, every emotional experience triggers an opposing reaction. For example, feeling intense joy may be followed by feelings of sadness or discomfort, as the body seeks to maintain emotional balance. This theory was proposed by Richard Solomon in the 1970s and is often used to explain various phenomena, such as addiction and the experience of color vision. In the context of color, it suggests that colors are perceived in opposing pairs, like red versus green and blue versus yellow.