Ethereal Gin is a special limited-edition, small-batch gin made by Berkshire Mountain Distillers. Each edition gets a different colored label.
The latest batch as of this writing is numbered 6 on the back of the bottle, and it has a blue label. I have seen numbers back to Batch 4, and unnumbered pink and orange labels, so I do not know the order of those two, nor what is the color of the missing label.
I had a chance to sample the five shown above all side-by-side in June 2012 at Perigee, a restaurant just outside of Stockbridge, MA. That report is on its own page.
I later got my hands on Ethereal 7 and was not disappointed. It has a very intensely citrus flavor of the lemon/lime but not orange character. It surely will be good with tonic water, but I really liked it in a Monkey Gland, too. I know now that I'll have to try each new Ethereal Gin as it comes out!