This study aimed to investigate the effects of different light qualities on the morphological development, photosynthetic characteristics, stomatal structure, and yield of potato, providing theoretical and practical guidance for optimizing light environments in controlled agricultural systems and enhancing the efficient production of potato microtubers. Six light qualities—white, red, blue, green, far-red, and ultraviolet—were applied to systematically evaluate their effects. The results showed that light quality significantly influenced plant morphological traits and physiological metabolism. Red and blue light demonstrated the most pronounced promotive effects. Under red light, plant height and stem diameter increased by 57.47% and 31.10%, respectively, compared to white light, while single tuber weight increased by 20.09%, despite a 14.96% reduction in tuber number per plant. Blue light significantly enhanced chlorophyll content (by 20.35%) and stomatal density (adaxial stomata increased by 28.85%), leading to a 38.98% increase in tuber number, a 51.79% increase in single tuber weight, and a remarkable 110.37% improvement in total yield per plant, compared to white light. In contrast, green light moderately promoted photosynthesis in lower leaves, but reduced the total yield by 39.90%. Far-red (740 nm) and ultraviolet light (390 nm) severely inhibited plant growth and failed to induce tuber formation. Correlation analysis revealed a highly significant positive relationship between chlorophyll content, net photosynthetic rate, stomatal density, and yield per plant (r = 0.96, p < 0.01). This study systematically evaluated the independent effects of single light quality on potato growth and production for the first time, clarifying the regulatory advantages of red and blue light, and providing important theoretical insights for optimizing the light environment with red and blue light to improve potato microtuber yield. Furthermore, this study provides critical data to support future research on the dynamic optimization of light quality ratio.