Did you ever resolve this? I have the same issue and I'd like to know which path to take.
I've had the tv for nearly 5 years, and I do not change the color, brightness, or contrast settings. When I turn it on, it briefly shows the color properly, for maybe 1-2 seconds. Then it suddenly brightens to the point where the colors look washed out or overexposed. The same problem happened to my sister's tv, with is the same model, just a few months ago (we got our tvs at the same time).
Is this fixable on my end, or would it need repaired? Or should I just start shopping for a new tv?