I found one website that said this: "There is something called "blood on the moon" and that is when there is a large red ring around the moon giving it a red appearence. The moon will pass completely into the shadow of the Earth producing a striking total lunar eclipse. The total phase throws an eerie reddish color across the face of the moon. The Earth's atmosphere acts like a prism, bending a little sunlight into the shadow and giving it a copper tint. In essence, what falls on the eclipsed moon is the light of all the sunsets and sunrises on Earth." It's also something that's suppose to happen before the 'end of days' in the Bible.