It's caused by Rayleigh scattering, which is by definition strongly
wavelength-dependent and is brought about by particles of the same order of
size as the wavelength of light, usually from fine dust or smoke. The blue is
scattered most so you see an orange/red moon (or sun, or planet, even, if it's
bright enough). Absolutely nothing whatsoever to do with refraction. Nothing
whatsoever to do with Saharan dust, which is too large to cause Rayleigh
scattering. Nothing whatsoever to do with ozone, whose scattering
characteristics are the same as nitrogen and oxygen. Very common indeed.
Happens all the time. Seen it thousands of times. Why the fuss?

Tudor Hughes, Warlingham, Surrey.