Auroras get their colors from specific elements in Earth’s upper atmosphere. Green auroras, for instance, come from atomic oxygen; blue is associated with molecular nitrogen.
How are the colors of the aurora created? The sun radiates all visible colors, which is why sunlight appears white. The spectrum of visible light associated with the aurora is much more restricted. The aurora is caused by charged particles in the solar wind colliding with atmospheric atoms and ions.
Why the different colors? The color of the aurora depends on which gas is being excited by the electrons and on how much energy is being exchanged. Oxygen emits either a greenish-yellow light (the most familiar color of the aurora) or a red light; nitrogen generally gives off a blue light…