<p>Color constancy is a fundamental perceptual ability of human color vision. The anchoring theory has provided important insights into human lightness perception; however, the specific anchoring rules underlying color constancy have remained debated for decades. In this work, we introduce a novel computational framework—gray anchoring (GA) theory—to explain how early stages of the visual system contribute to color constancy. We further demonstrate how the GA rule operates in the chromatic domain by identifying gray surfaces within complex scenes. Moreover, through quantitative analysis of the computational processing of concentric double-opponent (DO) cells in the primary visual cortex, we demonstrate a potential neural implementation of GA. Specifically, these cells may identify gray surfaces in color-biased scenes and thereby facilitate illuminant estimation in higher-level cortical areas. These findings provide not only a clear functional explanation for the concentric DO receptive fields in the visual system but also an effective and efficient solution for computational color constancy in computer vision.</p>