J, the problem is not related to the Matrix or
R-G-B color output circuitry thinking that if the Red & Blue output colors quit working, the Green color becomes dominant.
There has been some reports of Power Boards failure on some Panasonic professional and consumer model Plasmas since last summer mostly on the
TH-42PX20U/Y which I beleive it has been corrected on the current model
TH-42PX25U/P. There is also a possibility that your
TH-42PWD6UY was also utilizing the same power board which I am sure has been corrected also on the newer model
TH-42PWD7UY.
Whatever the problem is with your plasma,
don't waist anytime in getting it exchanged for one of the newer models.
Panasonic new line of plasma are listed right now on
www.panasonic.com