So is this midnight silver (steel) grey ?
Yes. That's it. Dolphin is quite a bit lighter and flatter. Here are the photos that sold me, per my PM to you. Just found them. The first is the one that did it for me. I didn't even see the color in the flesh before taking delivery and I have been very happy with it. Of course, it is all personal taste.
You can see how much lighter the Dolphin is. The Midnight has much more depth to it due to primarily to a bit of blue, and a small amount red, in the composition. It makes a dark (some would say boring) color pop more than one would expect.