Have to disagree there. The Nexus 4 came in black and white and there's plenty of evidence the Nexus 5 will as well. When the link in the Google Play store was active, it specified "black," which devices without color options do not:
https://play.google.com/store/devices/details?id=nexus_5_black_16gb
I'm expecting a black front and white back, as seen in the packaging and in one of the earlier leaked images (the phone on the left):
Personally, I prefer black, but just wanted to put it out there.