Most of Concrete Minerals' shades were "regular line" releases, until the limited-edition Arkham collection. Three of the four shades were okay, nice enough, but kind of close to colors already in CM's inventory. The fourth color initially didn't grab my attention...until I got the collection and swatched it. It's a yellow-ish looking grey in the pot that kind of resembles wet cement. Applied, though, it definitely shows its blue tones. This was added to Concrete Minerals' regular collection in November 2011, so even if you completely missed the Arkham collection you can still pick up this shade.