Change light color when entering trigger

Hi :) I'd like to change the color of a spotlight by walking into a trigger but it doesn't work. What did I do wrong?

 var licht : Light;
 
 function Update () {
 
 }
 
 function OnTriggerEnter(col : Collider) {
     if(col.tag=="li") {
       licht.Color = Color.red;
     }
 }