Definitely not dark green - much more of a blue actually. Looks like it might be some sort of chainmail armor, color combination R=20 G=70 B=100 (for those of you with LoY go to your dye window and type in those numbers for red, green and blue and you'll see exactly what color it is).
They can drop off of any of the Western Waste Dragons. Mine dropped off of Mazi, but random pieces of Dragon armor drop randomly off of all of the named Dragons.