LOL, but what looks best in in the eye of the beholder. I have used blue, and in general think it looks best. I however dont agree that it is natural or has any effects other than for veiwing.
As for the air quality, I dont remember. The orange moon is not a dialy sight, moonlight is generally white to the eye, though most references I can find report moonlight generally around 4000K (which is starting to get into the orangish/yellowish side of white). Those pictures were very low on the horizon when the moon seems unusually large and dull, only a couple times a year is it like that (atleast for the more orange one anyhow). When low in the horizon the shorter wavelegnths of green and blue are more scattered in the atmosphere, making it appear orange. Yes pollution will increase this effect, or simply the increase of dust and particulate in the air from farmers during the 'harvest moon'. I have pictures of the moon much whiter from a typical day, but they are washed out. I dont however have any natural pictures of the moon that are very blue

:
Here is the moonlights (I burnt up

) on my 75g:

I found that with blue most of my plants looked colorless along with the driftwood, rocks, and any fish that wasnt either white or blue. Made neon tetras really pop though.