This case study investigates the influence of interior lighting on consumer behavior within retail environments, focusing on how lighting affects mood, perception, and purchasing decisions. It begins by establishing the importance of retail design and the role of lighting in creating engaging shopping experiences. The study reviews historical context and the evolution of supermarkets in Sri Lanka, analyzing key players like Keells, Glomark, and Lanka Sathosa, and their lighting strategies. It also covers various types of retail lighting, including ambient, task, accent, and decorative lighting, and their impact on consumer responses. The methodology involves consumer questionnaires and case studies of the aforementioned supermarkets, analyzing location, interior design, layouts, colors, and lighting. The research aims to identify age and gender-related differences in market preferences and to scientifically assess how lighting designs influence consumer behavior and satisfaction. Ultimately, the case study seeks to provide insights for retailers to optimize their lighting strategies to enhance the shopping experience and boost sales.