Auroras result from emissions of photons in the Earth’s upper atmosphere which differ with altitude. At high altitudes oxygen red dominates, then oxygen green and nitrogen blue/red, then finally nitrogen blue/red when collisions prevent oxygen from emitting anything.
Green is the most common color. Then comes pink, a mixture of light green and red, followed by pure red, then yellow (a mixture of red and green), and finally, pure blue.
The intense auroral display in Murmansk was triggered by a CME strike on Saturday, December 19, 2015.
The impact resulted in intermittant G1 and G2-class geomagnetic storms for nearly two days opening a window into winter darkness.
Here some other northern lights captured on December 20, 2015 in Alaska.