Not that I can see.
It seems the shadows adopt the renovation status of the element they fall on and not from what casts them.
So Graphic Overrides and Renovation filters are not an option here.
You can't even select the shadows to change them manually.
We encountered a similar scenario, we wanted to indicate how much shade the proposed addition was going to cast.
One method that might get you close is to have a duplicate of your 3D document.
1st 3D Document set to only show new elements, and then adjust shadow foreground colour.
2nd 3D Document set to show new and existing, or existing and demo depending on your required output, adjust foreground colour.
It's not perfect as you still need to either stack drawings or use a worksheet to extract fills, or magic wand fills.