Gun metal grey is a dark grey (about few shade lighter then black) colour that have a bit of metallic finish, its a very popular factory colour for the R32 GTR & i don't think i have to explain silver right?
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having bought one from the FTO shop, my personal recommendation would be to buy the original one as a spare part through Mitsubishi. It will cost a little more but it's a better product.
The issue I have found with the after market ones is that the clear rubber becomes a little cloudy over time and can also become scratched, which can make it look a little strange.
From memory Scracy has a gun-metal grey, original Mitsubishi one on his car.
Just remember these are a sticker, not made of chrome or anything...
Its hard to describe, but its one of those 'puffy' style stickers.
I think it looks good, and not bling bling - havent seen a 'grey one' but it might look a bit more like a sticker... sorry if that post doesnt make much sense, but hard to describe