To investigate the effects of photoperiod on population growth of the red and green color morphs of the pea aphid Acyrthosiphon pisum (Harris), the development, reproduction, and life table parameters were examined for various photoperiods (22 L:2 D, 16 L:8 D, 10 L:14 D, and 4 L:20 D), controlling for light intensity (103 μmol m^-2 s^-1). For the 22 L:2 D photoperiod, the red and green color morphs of the pea aphid had the highest nymphal survival rates (90.28% and 88.89% respectively), the shortest duration of development (5.63 d and 6.26 d), the highest net reproductive rates (49.3472 and 47.8103), the highest average fecundity (54.56 and 55.16), the highest maximum fecundity (121 and 112 offspring per female aphid), and the highest intrinsic rate of increase (r_m =0.3263 and 0.2863, respectively). Population growth was higher for the red color morph than the green color morph for the 22 L:2 D photoperiod. For the 16 L:8 D photoperiod, the red color morph of the pea aphid had a higher nymphal survival rate (72.22%) and shorter adult longevity (6.58 d) than those of the green color morph (69.45% and 7.08 d, respectively). However, the green color morph had a higher intrinsic rate of increase (0.2648 vs. 0.2249), indicating a higher population fecundity of the green color morph than the red color morph for the particular photoperiod. For the 10 L:14 D photoperiod, the red color morph had a higher nymphal survival rate (80.55%) and intrinsic rate of increase (0.2490) than those of the green color morph (79.17% and 0.2277, respectively). However, the green color morph had a longer duration of development (7.92 d) and adult longevity (12.71 d) than those of the red color morph (7.60 and 6.88 d, respectively). For the shortest photoperiod (4 L:20 D), the red and green color morphs of the pea aphid had the lowest nymphal survival rate (64.67% and 35.50%, respectively) and the longest duration of development (13.26 and 13.61 d). Moreover, the red color morph did not produce offspring and had a fecundity of zero. However, its intrinsic rate of increase, -0.0366, indicated negative population growth of the green color morph. In conclusion, extremely short durations of light (4 L:20 D) can prolong development and adult longevity, but reduces nymphal survival rate and the intrinsic rate of increase of two pea aphid color morphs. However, extremely long durations of light (22 L:2 D photoperiod) resulted in shortened development and decreased adult longevity, but an increased nymphal survival rate and fecundity for the two pea aphid color morphs. Moreover, the 10 L:14 D photoperiod was a more suitable condition with respect to population growth for the red color morph, but for the green color morph a photoperiod of 16 L:8 D was better. Therefore, the results of this study may facilitate artificial breeding of pea aphids and the prevention and treatment of pea aphid attacks on field crops. Furthermore, the mechanism underlying the response to photoperiod differed between the red and green color morphs of pea aphids. Further studies are needed to examine these mechanisms.