I was fortunate enough to be one of the lucky folks to get a free bottle of Essie "One Day Without Blues" courtesy of Essie and TOMS shoes, as part of the recent "One Day Without Shoes" drive to draw attention to the less fortunate around the world.
I've seen a few reviews around of this lovely cornflower blue, and apparently it's the exact same thing as Essie "Coat d'Azure," so don't freak out of if you didn't get it.
It struck me, though, as very similar to a certain Zoya I have, Jo. So, in trying to cram gardening AND swatching into the waning daylight this afternoon, I hastily slapped on a couple of coats of Jo next to my (terrible) Essie ODWB mani for your comparing pleasure.
That's Essie on the left, and Zoya on the right. Excuse the pseudo-baldspots on the Zoya; that should give you some indication of how much more sheer it tends to be than the Essie. Jo is much more shimmery, too. ODWB is almost a total creme, if it weren't for the faintest hint of shimmer. You can really see a shimmer in the bottle, and a slight flash of purple, but this effect is greatly reduced on the nail...you probably can't even see it in the picture. Long story short, these are definitely not dupes, and I can never have enough cornflower blues!