In this article, the authors present a model for color images. Specifically, they show that the color channels of an RGB image can be written as a color-dependent local mean multiplied by a color-independent residual. This model is derived from a generalized class of image formation models. The authors present experimental results showing that this model accurately describes images from a Sigma DP1 camera, a Pentax K-3 II camera, and the Kodak dataset. They also discuss how this model can be used to design a simple chrominance-based denoising system and present results for that system.