The colour of base edgings was a topic on another website I was involved with last year. Much of the debate hovered around what looks best on the wargaming table and the concensus appeared to be that brown shades fitted the bill best.
Green was, I remember, the colour of choice in the early days of the fantasy hobby, largely because the GW studio team used this most often.
I did a survey of a website set up by a collector of miniatures in which over 100 painters, as opposed to wargamers, were represented. Of these the count was in favour of black which substantially outnumbered the second place, green, which was well ahead of brown in third place.
My view is that if you are wargaming, a neutral base colour to blend with the terrain would be preferred. As a painter my preference is for a colour which will not detract from appreciation of the miniature and black is my choice with dark brown a close second.