I am new to Blender and looking for your help: The problem: In my scene are many blue objects (e.g. spheres) and multiple cameras. I want to color every surface of the blue objects red, if they are visible from at least one camera. All hidden objects from all camera views stay completely blue. Some blue objects are only partially visible to the cameras and only these visible surfaces turn red (the rest stays blue). Blue objects, whose whole surfaces are covered from the cameras, turn fully red. How could you easily implement that?