InvalidProgramException: Invalid IL code - when using static function

I don't know if this is causing the error, but you are calling an instance method from your static function.

 // RenderScript.js
 static function DoRender(c:Color){
     var childrenRenderer : Renderer[];
     childrenRenderer = GetComponentsInChildren.<Renderer>();
 
     for (var childRenderer : Renderer in childrenRenderer) {
         childRenderer.material.color = c;
     }
 }

GetComponentsInChildren.<Renderer>() is an instance method. You can't call it without having an object and since you are using a static method, there is no instance. You will need a different way of gathering all the renderers, maybe making a singleton and then accessing the renderers through that.

How to implement a singleton in js. You can do it with properties if you want to but it isn't really necessary.

 //Singleton.js
 private static var rendererParent : GameObject;
 
 public static function GetRendererParent () : GameObject {
       if(rendererParent == null) {
            rendererParent = GameObject.Find("Some GameObject");
       }
       return rendererParent;
 }

then find the instance using GetRendererParent() and call GetComponentsInChildren() with that. Note that this will always use the same instance, thats why its a singleton. If you want to be able to change the game object, then you will need to do something different such as pass the parent into the function.

Edit:

If the parent object is varying, you probably don't want it a singleton. Your code was close, but you want to pass the reference to the game object into the function.

 //Not a Singleton
 public static function DoRender (_objectName : String , c : Color) {
 
     var  rendererParent = GameObject.Find(_objectName);
     //Find a GameObject with the name you pass into the function.
 
     //gather all the renderers in its children.
     var childrenRenderer : Renderer[] = rendererParent.GetComponentsInChildren.<Renderer>();
 
     for (var childRenderer : Renderer in childrenRenderer) {
 
        childRenderer.material.color = c;
 
     }
 }

or an overloaded method that takes the game object directly. The compiler can infer which method to use based on what arguments you pass.

 //overloaded method.  Takes a GameObject and a color rather than a string and a color.
 public static function DoRender (_object : GameObject , c : Color) {
 
     //gather all the renderers in its children.
     var childrenRenderer : Renderer[] = _object.GetComponentsInChildren.<Renderer>();
   
     for (var childRenderer : Renderer in childrenRenderer) {
 
        childRenderer.material.color = c;
 
     }
 }