Painted in 1508, Raphael's “Saint Catherine of Alexandria” is animated by innovative pictorial techniques using light, shadow, and color. Yet scholars have scarcely discussed its dazzling palette or sought to explain the image's meaning. I argue that Raphael's “Saint Catherine” exemplifies the artist's thematic interpretation of divine revelation in optical terms. Aristotelian theories of vision illuminate new dimensions of Raphael's engagement with scientific and theological sight. From this examination, new criteria for identifying the painting's patron emerge. By reframing the “Saint Catherine” within the rubric of contemporary optics, color's role as an allegory for Raphael's subject comes increasingly to light.