[UNET] How to configure a level gameObject?

Hello everyone. I wish you happy new year. I have an issue. I'm working on a Unet (network) unity project and my aim is to have a client side "Button" that act on a level cube object (changing its color for example). -Every client (player) will have his own button, and onClick it will change the color of the cube. -I don't want to my cube to be created/spawned by a script. I tried this solution: 1) The button have a network identity with local authority, a network behavior script . 2) The second button ("Interrupteur") (or cube) have a Network identity and a script with Rpc method. This solution sadly doesn't work. Do you have any idea? I've read the unity articles and I was really confused. Does my client button have to be a player prefab?? What about my cube (or "Interrupteur button")? Does he be set without a networkIdentity? (my cube is part of the level) Thank you for your answer.