My original fat PS3 has an option to set deep color over HDMI,
Quote 'xvYCC is significant ONLY if all components in the chain support xvYCC. Do not utilize this setting on any component unless everything else can fall into place. Once set, xvYCC should override and RGB or YCbCr settings.'
This is true, but according to this article discussing HDMI 1.3 and the inclusion of deep color:
Neither HD DVD nor Blu-ray support xvYCC or Deep Color, and never will. Those features are beyond the spec of either format.
Long story short, even if you have a brand new HDTV that can actually render all of those billions of new colors (most can't), and even if you have HDMI 1.3 connections on both ends and every piece of equipment in-between, you'll simply never get those colors from a Blu-ray or HD DVD source. Maybe in some other type of product (like an HD camcorder or video game) or some future movie format, but not from HD DVD or Blu-ray.
The article goes into more detail about why this is so. Something may have changed in the Blu Ray spec since this was published three years ago, but if not, deep color/xvycc should be a non-factor regarding Blu-ray output, and if available, should probably be disabled for Blu-ray playback.