In this paper, we discuss the use of computer graphics techniques to model and explain the structures commonly observed in color histograms of images. This includes an accurate simulation of the physical reflection and transport behavior of light energy within 3D environments, the precise modeling of an image capturing system, and an interactive visualization module to display color histograms. Based on the fundamental rendering equation that describes light reflection and transport in the 3D world, we classify the color histogram structures of color images, and relate them to various physical components in image formation, including scene illumination, material reflectance properties, and the surface geometry of objects. We further show how these histogram structures can be effected by the artifacts caused by the limitation of image capturing systems. Our results demonstrate that the use of accurate simulation procedures under a precisely controlled computer graphic environment can clearly illustrate the causes of the structures observed, and can provide unique insights and explanations of image formation.