A sample of hydrogen gas confined to a tube is initially at room temperature. As

A sample of hydrogen gas confined to a tube is initially at room temperature. As the gas is heated, the observer notices that the gas begins to glow with a pale pink color. Careful study of the spectrum shows that the light spectrum is not continuous. Instead, the hydrogen gas is only emitting visible wavelength photons of four specific colors, which combine to form the overall color to the human eye. What is the best way to explain this behavior