Why do different noble gases glow in different colors when electricity passes through them?

When electricity passes through a noble gas confined at low pressure in a glass tube, the electrical energy excites the gas atoms, causing their electrons to jump from their ground-state energy level to a higher energy level.12

As these excited electrons return to their ground state, they release the excess energy as photons, which we perceive as light. Each noble gas has a unique atomic structure with specific energy levels; consequently, the energy difference between these levels varies for each element. Because the wavelength—and thus the color—of the emitted light is determined by the amount of energy released during these electronic transitions, different noble gases produce distinct colors. For example, neon emits a characteristic orange-red glow, while xenon emits a blue light.321