Okay, this how it works. You know those ND things in the tables? Those specify which colors are not to be faded out by the sun. They are to remain at the same intensity as they are on the model.
Unfortunately, this was only ever available in FS1 Software and both FS1 and FS2 Glide mode. D3D does not support it.
If the source code was released, this is definately one of those things to do.