They're actually Black (as opposed to gray). And me too! However, that was a decision simply made from a wholesale logistics/pricing point of view. I'm not really set up to offer that level of complexity on such a large scale and still make a profit due to the cost of having to have each custom material on hand in bulk quantity, and more importantly afford the labor costs from the constant machine setup, production etc. Hope that helps to shed some light on the situation.
But the other colors are available from my site! And I'd be happy to honor Massdrop pricing for your build if you just drop a comment with your order :)