The relationship of ground color to maturity was examined for 13 cultivars of peach [Prunus persica (L.) Batsch]. Samples representing a range in maturity for each cultivar were tested for flesh firmness and surface ground color at harvest. After ripening, the same lots of peaches were measured for ground color, soluble solids, titratable acid, taste, and visual appearance. Color was measured with a colorimeter in Hunter “L”, “a”, and “b” color coordinates and compared with a series of color references. Peaches selected as being of threshold maturity at harvest, based on taste ratings and firmness, showed average ground color readings of L = 61.2, a = −5.4, and b = 26.8, with results for individual cultivars narrowly distributed in this region of color space. Differences in ground color for varying maturities occurred primarily in the “a” coordinate, which increased as maturity advanced. On average, ground color was a better at-harvest indicator of edible quality after ripening than flesh firmness. Color references used for grading in California did not match actual ground color measurements for peaches grown in South Carolina.