Remote photoplethysmography (rPPG) can be used to measure cardiac activity by detecting the subtle color variation of the human skin tissue using an RGB camera. Recent studies have presented the feasibility and proposed multiple methods to improve the motion robustness for the subject movements. However, enhancing the signal-to-noise ratio (SNR) of the rPPG signal is still an important issue for the contactless measurement. In this paper, we conducted an experiment to study the lighting effect on the SNR of rPPG signals. The results point out that different colors of light sources provide different SNR in each RGB channel. By providing the dedicated light sources (λ= 490-620) nm, the SNR of rPPG signals captured from the green color channel can be enhanced. Among the tested light sources, light green provides the most significant improvement from -11.09 to -6.6 dB compared with the fluorescent light.