The Nexus 6 has been bit elusive ever since it launched. It's difficult to get the phone at all, let alone in the variant of your choice.
If you've been waiting to purchase the phone in the US, you should not go check out the Motorola website (link below). All four models, that is the Midnight Blue and Cloud White, in 32GB and 64GB each, are available for purchase.
As before, the 32GB model will set you back by $649.99 and the 64GB at $699.99.