Amazing Northernlights
Most Northern Lights are green in colour but sometimes you'll see a hint of pink, and strong displays might also have red, violet and white colours. The reason for the why most of us see the green colours are mainly two, the first of which is that the human eye detects green more readily than other colours. This is why photographic images of the Northern Lights will often show colours that were not visible at the time to the naked eye.
However, the main factor in determining the colours of any given display is the altitude at which the solar particles collide with our atmosphere. Different gases prevail at different altitudes and in varying concentrations and it is the collision which “excites” these gases that determines the colour of the Aurora.
We don’t see red/pink in the Aurora Borealis too frequently and the colour tends to be associated with intense solar activity.