Just got back from my try-on appointment and can confirm that the Apple watch Space Gray is definitely darker than iPhone 6 Space Gray. I would call it more like Space Charcoal but that probably doesn't sound as cool. What really caught my attention was that the employee who was assisting me repeatedly referred to it as "Space Black" when talking about the Space Gray Sport watch. Holding my iPhone 6 up to the watches I would say my phone was a shade darker than the lighter colored Sport watches but significantly lighter than the Space Gray watch.