I have been watching this thread with a lot of interest. I have a Phillips 50" plasma, and I have been living with bizarre colors for six months. There are so many bad effects that I no longer believe that any color I see on this TV is correct.
You can see some pictures of my set here
My set has had its picture processor board replaced with no effect. Currently a new replacement plasma panel (including all its power supply and driver circuits) is on the road toward my local service center. I do not see this problem as likely to be display-related, but more likely something (including software) defective in the picture processing stage. I should know about the results of the panel replacement by Friday.
I encourage all of you--including those who have not seen this problem--to download the test files included with my pics and see what comes up on your screens. There is a color ramp included that should appear on your TV just the same as it appears on your computer. If that does not happen, please describe your results here--with pictures if possible. You can display the files from a memory card, USB memory stick, or a connected computer through any HD connection.
There was an early post in this thread indicating a narrow purple band showing up in a gray test ramp. That would be your snake when it appears in a normal image. And how do you get purple (red plus blue) when it should not be there? Well, that comes from an absence of green, so look for a dark band in the green test ramp.
The pictures I have seen in this thread look pretty much like the images on my TV. I am suprised by the focus on "purple snakes", when your pictures show large areas of inappropriate green, and skin tones demonstrate lots of green and red posterization--like on my TV. Do you also see streaks of yellow in cloud scenes? That would be caused by a blue drop-out.
Another thing to check. I can fairly well disguise the mis-colorization of my picture by selecting any auto picture mode. This is because: (1) the auto modes (like "Vivid", Rich", Multimedia") lower the brightness so much that about 25 per cent of the gray scale goes black, and there is no low-brightness detail; and (2) the auto modes also raise the color level so high that skin tones for all white persons turn a deep orange. There will still be some colored posterization, but it is fairly well concealed. I can totally swamp out the posterization by using a color setting of 100 (the proper setting is 22), but then every person looks like a character in a Simpsons cartoon. And of course everything glows.
I mention this because some of you who own the kind of TV that has shown problems for others, but have not seen it yourself, may be hiding the problem by overcooking your display settings. Like--to get a "punchy" picture. As a test, you can try setting the color to zero, and see if there is any colorization of the remaining black-and-white picture. When I do this with my TV, there is still plenty of bad colored posterization left.