They are actually the result of collisions between gaseous particles in the Earth's atmosphere with charged particles released from the sun's atmosphere.
Differences in colour are due to the type of gas particles that are smashing against one another. The most common auroral color, a pale yellowish-green, is produced by oxygen molecules located about 60 miles above the earth.
Rare, all-red auroras are produced by high-altitude oxygen, at heights of up to 200 miles. Nitrogen produces blue or purplish-red aurora. We know that sun is a large mass of hot gases and the amount of temperature can be said to be near millions of degrees Celsius.
