Targeting retical that changes color

I have this code for a targeting rectical that changes colors but im hiting the following errors.

ArgumentException: You are not allowed to call get_transform when declaring a variable. Move it to the line after without a variable declaration. Don't use this function in the constructor or field initializers, instead move initialization code to the Awake or Start function. Targeting..ctor () (at Assets/Targeting.js:6)

This is my code for it>

 var crosshairTexture : Texture2D;
 var crosshairRange = 200;
 
 private var hit : RaycastHit;
 private var facingDirection = transform.TransformDirection(Vector3(0,0,1));
  
 function Update () 
 {
     if (Physics.Raycast(transform.position, facingDirection, hit, crosshairRange))
     {
         if(hit.collider.gameObject.CompareTag("Untagged"))
         {
             if (hit.collider.gameObject.CompareTag("Enemy"))
             {
                 crosshairTexture.color = Color(1, 0, 0, 0.5);
             }
  
             else if (hit.collider.gameObject.CompareTag("Friend"))
             {
                 crosshairTexture.color = Color(0, 1, 0, 0.5);
             }
  
             else
             {
                 crosshairTexture.color = Color(1, 1, 1, 0.5);
             }
         }
     }
 }