We were suspicious of the image, and we grew even more suspicious when we received a tip pointing to images that were clearly modified versions of the black Nexus 5 press render, but showed the device in various colors like purple, orange, red, and silver. Just after that as we were starting to look at the render of the pure white Nexus 5, Android Police posted the rumor smash explanation, meaning we didn't have to finish our research.
As AP points out, the pure white Nexus 5 is nothing more than the black version with inverted colors on everything except for the camera lens and flash. To prove how easy it is to make a fake like this, they made a gif, and some other color variants. We've also added in the other fake color renders, just so you have it all in one spot, and we don't need to deal with the rumors again. All of these are fake, but it definitely makes us eager to see Google offer the Moto X color customization on a Nexus device.
source: Android Police & Imgur