Final answer:
Cu²⁺ gives off higher energy photons when it gives off green light compared to Li giving off red light.
Step-by-step explanation:
The higher energy photons are released when Cu²⁺ gives off green light compared to when Li gives off red light.
Energy of a photon is inversely proportional to its wavelength, so shorter wavelength photons have higher energy.
Cu²⁺ complexes have a vacancy in the eg orbitals, and electrons can be excited to this level, resulting in absorption of visible light and emission of higher-energy photons.