Custom Content has Orange Shadows/Blown Highlights in Game

I had a look at your files and could see nothing wrong at all. However, you used a plant for the clone, I use a purple spec for leaves and I have not ever had your iridescent effect, (I like it by the way for plants). I'm wondering if changing the clone to an object might solve the problem? Although you said all objects... I know that bright sunlight can affect object colour, the light in the Sylvan Glade for example will turn everything pink and the winter light makes all the plants (and everything else) a revolting brown. Maybe the light connected to the time of day/season/neighbourhood is having a effect outdoors?  I have used a black vertex paint to test objects, could be worth a try?