Any image depicting the [[moon]] with a distinct red tint or glow.  Also called a "blood moon."  This is often considered an evil omen.

In real life, the moon turns red during a total [[lunar eclipse]] because sunlight is completely blocked by [[Earth (planet)|]] and the only light reflected from its surface has been refracted from Earth's atmosphere, which is red in color for the same reason that a sunrise or sunset turns the sky red.
血月