The expansion of human activity into natural habitats necessitates the introduction of artificial light at night, which can severely impact local fauna. In recent years, advances in LED technology have enabled the spectral tuning of artificial light sources, which could in theory limit their impact on vulnerable organisms. However, resulting experimental comparisons of candidate eco-friendly colors have mostly considered only one type of fitness effect, and often on only one species. Herein we expose synchronously flashing Photinus carolinus fireflies at a popular ecotourist site to downwelling illumination of three colors (blue, amber, and red) and record the impact on male courtship flash activity, as well as the degree to which the lights attract flying insects. Our results suggest that spectral tuning has been overpromised as a conservation solution. Instead, dimming, shielding, and otherwise limiting artificial light in both space and time is likely the best method of minimizing its impact on natural habitats.