If your player is sending the patterns from the AVS disc out as 601 when they are encoded as 709, it is likely making things harder for you. The player is twisting the disc's 709 colors to the 601 colorspace, and then the Edge is re-twisting them back to 709. This involves a lot of math and depending on the precision in each component, something may be lost or skewed a bit in the process.
I'll definitely take a look at that AVS HD thread. I wasn't aware that others were seeing the same thing you are. Out of curiosity, what is the Edge reporting as the input colorspace when you are viewing commercial Blu-Ray content?
I think your major issue, though, is your display's color decoder. As delivered, Mitsubishi sets have some really off-spec color decoders (we have a 46807 CRT RPTV, so I'm familiar with this). Even the Mits PerfectColor menus won't get you fully accurate color, but you can get close. The AVS disc thread mentions some PerfectColor settings from CNet for another Mits DLP, and those might get you in the ballpark.
IMHO, you have several obstacles here: the double colorspace conversion (may not be a big issue), filters which probably don't match your primaries, and an out-of-spec color decoder. But you can get there, or nearly so.