he Earth, Sun and Moon are almost exactly in line and the Moon is on the opposite side of the Earth from the Sun.
As the full Moon moves into our planet's shadow, it dims dramatically but usually remains visible, lit by sunlight that passes through the Earth's atmosphere.
As this light travels through our planet's gaseous envelope, the green to violet portions get filtered out more than the red portion, with the result that light reaching the lunar surface is predominantly red in colour.
Observers on Earth may see a Moon that is brick-coloured, rusty, blood red or sometimes dark grey, depending on terrestrial conditions.