The only thing that looked different when switching from default render settings to optimal in MPC-HC was that the chroma got shifted like half a pixel to the right.
A weird thing though, that might indicate the file itself does have the correct colors, is that when making a script like this:
DirectShowSource("Despecialized Edition v2.0 Final Workprint.mkv")
Opening it in MPC-HC and Avspmod both gives a correct color result.
When opening the file itself in MPC-HC it shows the orange-ish reds. Maybe the codec converts the color, and when using DirectShowSource in a script it bypasses that?