As the core expressive elements of oil painting, the interplay between light, shadow, and color profoundly shapes a work's visual appeal. This study employs theoretical analysis to systematically explore how these elements influence the visual expressiveness of oil paintings through their regulatory mechanisms. The findings reveal that light-shade-color relationships impact oil paintings' visual effects through four dimensions: spatial depth creation, rhythmic composition control, emotional atmosphere transmission, and visual impact intensity. Key approaches to optimizing visual expressiveness include enhancing light source techniques, refining chiaroscuro arrangements, adjusting color temperature, and achieving precise balance in contrast relationships. The scientific application of light-shade-color relationships significantly enhances the artistic impact and aesthetic value of oil paintings.