[VIDEO] RAYLEIGH SCATTERING explained by Professor Emeritus Walter Lewin at MIT (and more) For The Love Of Physics. I recommend watching the whole lecture from beginning, the part on color starts at about 28:00 http://youtu.be/SRh75B5iotI?t=27m56s
Blood moon. The reason why the Moon takes on a reddish color during totality is a process called Rayleigh scattering. This is the phenomenon responsible for the sky to be blue and the sun to appear yellow.