No. Dark Sky Metallic looks identical to Cadillac's Shadow Metallic.
We were looking at two new Cadillac CT5 cars yesterday, one was Shadow Metallic. The Shadow Metallic was a very blue grey. I was comparing it to the other CT5, painted Satin Steel Metallic. It was very obvious that the Shadow Metallic while a dark grey, had a very blue tone, while the Satin Steel Metallic was very grey, with a brownish tone. This was in broad daylight, under an overcast sky.