Color constancy is often defined as the ability to perceive object colors that are stable against changes in the spectrum of the illuminant. This definition leads naturally to experiments and theories where the independent variable is the illuminant spectrum. A more general definition, however, emphasizes that other factors also influence object color appearance. Such factors include the reflectance and location of other objects in the scene, the illuminant geometry, and the shape and pose of the object being judged. How should the richness afforded by these additional factors be incorporated into our study of constancy? I will review work designed to clarify the joint influence of the illuminant spectrum and the spectral reflectance of other objects in the scene on the color appearance of a test object. Observers adjusted a test object to appear achromatic under different illuminants and when the test was surrounded by different objects. Both factors influenced the achromatic locus. The data are explained by a model based on the idea that an estimate of the illuminant governs the relation between the light reflected from the test object to the observer and the color appearance of the test. The model's estimate depends both on the actual illuminant and on the reflectance of the objects in the scene and thus can account for the effects of both factors. Acknowledgments: Peter Delahunt, William Freeman, James Kraft, Philippe Longére, Shannon Maloney, Melissa Rutherford, Jon Speigle, Agilent, Inc., and EY10016.