The above post was before the XBR4 and XBR5 even existed to my knowledge. I think RGB FULL, Deep Color & xvYCC are all pretty much the same thing and are just terms/features referring to the RGB color space from 0 to 255.
I believe the only displays that support RGB FULL are computer monitors that will display 8-bit RGB from 0 to 255 and HDTV displays that support xvYCC (aka Deep Color? / RGB FULL?) which is RGB from 0 to 255 (I think the only xvYCC HDTVs are 10-bit displays currently).
I just got my 46" XBR4 (Nov 2007 build date) and after calibrating the last few days, I can indeed report that the XBR4/5 *AND* the PS3 should be set to RGB FULL.
Keep in mind that (to my knowledge) all the components must support HDMI 1.3+ and xvYCC.
I now have everything in my chain HDMI 1.3a compliant (receiver, HDMI cable, PS3 and display).
I forced RGB to FULL (not OFF and not AUTO) on the display and the PS3. This will insure that the XMB and games output in RGB FULL (0 to 255) because this is what the XMB and games are encoded in. I also turned xvYCC on in my receiver. ***I had to turn the display, receiver and the PS3 off to reboot the devices after making this change.
Output on the PS3 for DVD/BD is set to YCbCr (BT.601 for SD-DVD / BT.709 for Blu-Ray which is RGB Limited or the RGB color space from 16 to 235). This is what SD-DVD and BD are encoded in. I also turn on SuperWhite since apparently some BDs use this.
There is a good Wiki article that explains what I am talking about:http://en.wikipedia.org/wiki/XvYCC
Everything works perfect now where as it did not with my older KDL-40V2500. With the older TV, once I turned on RGB FULL and calibrated the display, the XMB and games looked okay, but once I turned on a DVD or BD, everything was WAY too bright and washed out. This no longer happens with my XBR4.