The Northern Lights appear in different colors depending on the gases with which the solar particles collide. Generally, they appear in colors of green, yellow, blue, purple, pink, and red.
The most common color is green, due to the impact of solar particles with oxygen atoms. Blue, purple, and pink are rarer to see and are associated with solar particles colliding with nitrogen atoms. Red is the rarest color to see and is associated with solar particles hitting oxygen atoms but at a higher altitude above 150 miles.