[rdouglass]

Not my words but accurate AFAIK...

"The atmosphere plays a role here. Longer wavelengths pass through the atmosphere more readily, while shorter wavelenghts are scattered (related to the "why is the sky blue" question). When the moon or sun is low in the sky and shining through more atmosphere, this effect is at its maximum. Note that though the reddish appearance of the moon during the eclipse is related to this, an eclipsed moon can appear red when high in the sky."

So IOW it all has to do with the angle and the refractive qualities of the medium.