Editing color with C# script

Hi there,

I'm trying to use an UPNP Device to interact with my Unity Scene. I manage to do it but I encounter an error in the setter :

 public void CubeService_setColor(DvCubeService.Enum_color newColor)
         {                
             CubeService.setColor(newColor); // this allow me to save the color value in the script
 
             switch (newColor.ToString())
             {
                 case "red":
                     gameObject.renderer.material.color = Color.red;
                     break;
                 case "blue":
                     gameObject.renderer.material.color = Color.blue;
                     break;
                 case "green":
                     gameObject.renderer.material.color = Color.green;
                     break;
                 default: break;
             }
         }

The error is :

 InternalGetGameObject can only be called from the main thread.
 Constructors and field initializers will be executed from the loading thread when loading a scene.
 Don't use this function in the constructor or field initializers, instead move initialization code to the Awake or Start function.

Even if I initialize the value in the start function this error is still there...

Looking on other post I found a solution mooving the switch to the Update function and use a Getter for the value. And it actually work.

But for what I need to do after, I would prefere not using Update... Is there an other solution to invoke the color change only once in the setter ?

Thank you.