The lecture addresses two fundamental questions about color vision and aging. First, what are the mechanisms responsible for changes in chromatic sensitivity from infancy to old age? Psychophysical methods can be used to identify the optical and retinal origins of these changes, but also may serve as probes for identifying neural substrates. For example, a recent study demonstrated different rates of aging for detection of increments and decrements mediated by short-wave sensitive cones (i.e., putative ON- and OFF-pathways in the retina). This dissociation implies that detection of increments and decrements is mediated by different circuits. Second, why is color appearance so stable across the life span despite senescent changes in sensitivity of retinal mechanisms? For example, changes in unique hues, color naming, and the achromatic point all reveal a surprising degree of stability in color appearance across the life span. Changes in color vision following removal of a brunescent cataract support the hypothesis that the visual system continuously renormalizes itself to maintain constancy of color perception. These mechanisms have a more protracted time-scale than typically engaged by adaptation experiments in the laboratory, and compensate for sensitivity changes occurring in low-level mechanisms. Thus, an elderly person may call the same stimulus “white” as he or she did 70 years ago, even though it must be based upon a markedly different retinal stimulus and ensemble of neural activity.