Found this at Ulta after considering an online purchase of Zoya (after reading reviews).  Gemma is an army green color, and in the bottle, you can see the contrast dichroic-type effect of pale purple shimmer.  However, once it's on the nails, that dichro effect is lost.  It simply looks like a shiny army green.  I think that the difference between regular ambient light in a room (or outdoors) and the pale purple shimmer is simply not great enough to show a difference.  If you're looking for army green, go for it.  If you're looking for dichroic effect, keep looking.