Green auroras appear more frequently than red or blue ones due to two primary factors: the concentration of atmospheric gases at different altitudes and the sensitivity of the human eye to various colors.
Oxygen Concentration: Green auroras are produced when charged particles from the sun collide with oxygen molecules at altitudes of about 60 to 190 miles (100 to 300 km).
Higher Altitudes for Red: Red auroras occur at higher altitudes (around 180 to 250 miles or 300 to 400 km), where oxygen is less concentrated.
Nitrogen and Blue/Purple Auroras: Blue and purple auroras are produced when solar particles collide with nitrogen at lower altitudes (below 60 miles).
However, because nitrogen is less abundant at these altitudes compared to oxygen, blue and purple auroras are even rarer than red ones.
The human eye is more sensitive to green light than to red or blue light. This heightened sensitivity means that even when green auroras are less intense, they are more easily perceived, making them appear more frequently in observations
Photographic images may capture a wider range of colors, but the dominant visual experience for observers is typically green.