OnMouseDown, How to detect if the mouse clicks outside of the collider

Hello i have a major problem, im creating a strategy game and i have it so if i press on my “worker” then he will be “selected” and a blue ring shows under his feet, but i want it so if im clicking anywhere but now on the worker, then the ring will disapear. Any ideas? here is my script:
(JS)

#pragma strict

var SelectedRing : GameObject;
var Selected : boolean = false;

var showGUI : boolean = false;

var WorkerSpawn : GameObject;
var Worker : GameObject;

function Start ()
{
	SelectedRing.SetActive(false);
}

function OnMouseDown ()
{
	Selected = true;
	SelectedRing.SetActive(true);
}

function OnGUI ()
{
	if(showGUI == true)
	{
		if(GUI.Button(new Rect( 100, 50, 100, 100), "Spawn Worker"))
		{
			Instantiate(Worker, WorkerSpawn.transform.position, Quaternion.identity);
		}
	}
}

You could try setting up a ray

function OnMouseDown
{
    var ray: Ray = Camera.main.ScreenPointToRay(Input.mousePosition);
    var hit : RaycastHit;

    if (Physics.Raycast(ray) && hit.transform.gameObject == Worker) {
     Selected = true;
     SelectedRing.SetActive(true);
   }
   else
    //Clicked on something else

}