Later, they will jump back down to the ground state. When they jump back down, they give off electromagnetic radiation. If the radiation is in the visible range, then the atoms will glow. Some common examples are mercury or sodium lights. Mercury gives off a bluish-white color.
Sodium gives off a yellow color.
The atmosphere of the moon is sodium. The atoms of different elements give off different spectra. This is the basis of many ways to identify the presence of different elements. Each atom has a characteristic spectrum , which can be considered like a fingerprint . The spectra allow us to identify the elements.