I just switched to YUV422 mode after trying out the test pattern posted previously.Hmm, it seems like your display is getting the full 24 bit color information or else you would see some sort of banding. My feeling is that some displays shipped with the 24 bit color enabled, and others with the limited video color mode. Hopefully the setting is in the service menu somewhere, though it's also a possibility that it is a user inaccessible setting or even a hardware jumper.
houkouonchi, can you try setting your display output format to YUV422 and see if you see the same type of banding? I think that would confirm whether what we're seeing is the limited bit depth or not.
There's more detail in the blacks now and I definitely don't see the red issue with either mode. However I am talking about the 50 inch version so it might not apply to the 39 inch version.