Well, Vue is rendering right now, so I can't check myself. You use the yellow maple tree, right? What if yoy load a few yellow maples in a scene and see if the colour change is as big? I suspect the embedded colour shift in this plant might be the reason of these changes, if not due to your actions. If this is the case, then there is nothing you can do about it. It's a downside of Vue's procedural way of creating unique plants.