Earthquake lights are reported to appear while an earthquake is occurring, although there are reports of lights before or after earthquakes. They are reported to have different shapes with a white to bluish hue, but occasionally they have been reported having a wider color spectrum.
A different explanation involves intense electric fields created piezoelectrically by tectonic movements.
Another possible explanation is local disruption of the Earth's magnetic field and/or ionosphere in the region of tectonic stress, resulting in the observed glow effects from ionospheric radiative recombination at lower altitudes and greater atmospheric pressure.