Mystery solved. Oppo was set for RGB color space whereas the cable box was in YCbCr. Both standards convey the same information, but in a different way. The TV set doesn't have any setting referring to the color space, it accepts them both, but requires different settings accordingly.

Once I switched Oppo for YCbCr, the same settings work beautifully for both sources. Some TV channels may go astray, but not by very much, and I was always taking Discovery HD Theater as a reference for HD.

It's all the way it should be now, thank you, gentlemen, for your input. I sincerely believe that this forum is a true "feature" of Outlaw, they should print it in the user's manual.

Alex