A red aurora is a real phenomenon caused by charged particles from space interacting with the upper atmosphere. It requires more energy than a typical green aurora.
Red light is produced higher up in the atmosphere, around 200-300km, compared to green light which is lower at 100km.
Rare red auroras have historically been seen as ominous signs and portents of war or death due to their unusual color resembling fire or blood in the sky.
Very energetic solar activity can cause auroras to appear at lower latitudes and take on a red hue when viewed from those locations farther south.
Areas inside the Arctic circle like Svalbard can occasionally see faint red "day-side" auroras during polar nights, when the sun isn't visible at midday. These are caused by direct particle precipitation.
Auroras in general are caused by solar particles interacting with Earth's magnetic field, with color depending on the emission altitude and viewing location relative to the auroral oval.