There are multiple settings on my S64 plasma that deal with colors, gamut, pixel format, etc. I don't seem to have most of those options with my 6600K like I've seen with dedicated AMD GPUs (are my drivers or CCC messed up?), so I've had to set it up all in the TV.
I know there's one setting for blacks on my TV where you have to put it at "light" or else it crushes blacks. Then there's settings for something like photo, movie, etc. modes, which I either set to auto or off. Then you have the dedicated gamma setting. Normal vs. Native colors (native can be over saturated).
It's really weird how the picture settings work together on these plasmas, though I'm not sure how similar yours would be to mine (ST60 vs S64). I would focus on messing with all the picture settings on the TV itself.
I tend to forget to update these threads I create. My bad.
Your fix might very well be my fix: completely uninstall all AMD GPU drivers (you have an APU, correct? No idea if you would have to uninstall all AMD or just GPU only stuff), and I downloaded the latest beta release I think, but I think any version should be fine.
I got this from Nvidia diagnostic methods, but after uninstall, reboot first. Then, install latest version, or even the same version again, and then reboot once more.
Might even go as far as to use a driver cleaner in safemode, but you might not have to - this time, I did not have to.
After that, I was able to set the color output to 4:2:2 I think. I set the TV to "non-standard" for HDMI Color Range (or whatever that setting is) on the only HDMI input I am using.
That also helps because it works well to set the PS3 to Full Range with Super White and Deep Color (I believe I have those settings on the optimal configuration for this display's capability... could be wrong).
I'd recommend NOT making corrections at the TV level if you have bad colors, visible gradients, and black crush. You really won't be able to correct fully anyhow, and it'll make other input sources display incorrectly.
Ideally, the only two settings you need to make sure mesh up is setting the TV to either Non-standard or Standard (Limited Range? 16-235? Can't remember what they call it, but it represents the difference between using 16-235 and the full RGB 0-255 range).
Also, be careful not to really play around with adjustment sliders for desktop and/or video in Control Panel. Once you dial in the correct setting for Pixel Format on both ends, you should be getting the raw intended colors when using MCE or other media center software. I think you CAN make changes to the desktop colors, if you wish, without impacting how media in your media center application of choice displays. At that point, if things look off, that at least should be equal to what you see from other sources, and thus represent changes you need to make to the TV.