lunar eclipse
A lunar eclipse is a similar event to a solar eclipse, in which the Earth is positioned between the sun and Moon. While the Moon's real color is dark gray (with small variations from its geology), during a lunar eclipse, the only sunlight being reflected off the Moon is passing through Earth's atmosphere at an angle that turns it red for the same reason that sunrises or sunsets turn the sky red. In other words, the only sunlight reaching the Moon is the same sunlight being seen on Earth as sunrise and sunset, turning the Moon a pale red, often referred to as a "blood moon."
This tag implicates eclipse (learn more).