During a total lunar eclipse the Moon typically turns ##color(red){red}##.
That’s because the shadow of the Earth is not completely dark. Our atmosphere acts like a weak lens to bend or refract ‘s light slightly into the shadow — not a large angle but enough to let the refracted light reach the distant Moon directly behind the Earth. But as we see in the blue daytime sky not all of the light makes it through. Shorter wavengths get scattered away to make that blue sky; only the long red wavelengths make it all the way through the long trip through and go on to the Moon.
See http://earthsky.org/space/why-does-the-moon-look-red-during-a-total-lunar-eclipse.