A lot depends on the lighting under which one is viewing the Space Grey MBP.....in some cases it looks darker, in other cases it looks almost silver. When I first opened the box containing mine and removed the protective plastic covering it, I was at a table right under a chandelier and the lighting made the new machine look lighter than it actually is, to the point where I actually double-checked the labeling on the box and also grabbed my 12" MacBook, also Space Grey, for comparison, and then looked at my silver 15" 2015 MBP for a further comparison. When viewed in natural daylight, the Space Grey is definitely....Space Grey, not silver!

.
With regard to the question about putting a protective case on the MBP -- through the years I have never done that with any of my machines and they have always remained looking just great, no stains, no blotches, no discolorations of any kind, and no scratches, either. However, I am not a student or someone who carries a computer to school or work every day, or who participates in a lot of outdoor and indoor activities with the machine accompanying me everywhere. I do slide my. machines into a protective sleeve for transportation when traveling, but that is not all that frequent and definitely not the same as using an actual case meant to stay on it on a permanent/semi-permanent basis. A friend has a 13" MBP and he does keep it all the time in a protective case because he carries it everywhere and uses it in all sorts of environments, including on his boat, and wants his machine to always be protected, regardless of what he is doing and regardless of what situations he and the machine are in.