Dark Jade, Chalcedony and Shadow wotsit seem to take it in turn on my server (blood doodah had top position once), currently the green is the most expensive (but not horrific, maybe 10g a pop) and I have noticed I'm recieving less greens from prospecting ore - so I'll assume that coupled with it being one of the more needed colours hasn't helped.

Like a poster above, I have had more joy from Cobalt, which is handy as I have a low 70s miner alt working through quests in the lower zones so I'm keeping on top of my stash.