Need Help with color script

this script is suppose to fade from one color to the next. on my pc it dos not do this can someone look and see if every thing is correct

#pragma strict

var InFogColor : Color;
var InFogDensity = 0.0;
var lerpedColor : Color = Color.white;
private var LastInFogColor : Color = Color.gray;
private var LastInFogDensity = 0.0;
var Change = false;

function OnTriggerEnter (Col : Collider) {
   
   
    LastInFogColor = RenderSettings.fogColor;
    LastInFogDensity = RenderSettings.fogDensity;
    Change = true;
   
    //RenderSettings.fogColor = InFogColor;
    RenderSettings.fogDensity = InFogDensity;
}
function OnTriggerExit (Col : Collider) {
   
    Change = false;
    //RenderSettings.fogColor = LastInFogColor;
    RenderSettings.fogDensity = LastInFogDensity;
}

function Update() {

    RenderSettings.fogColor = lerpedColor;
       
    if(Change)
    {
        lerpedColor = Color.Lerp(LastInFogColor, InFogColor, Time.deltaTime);
       
    }if (!Change){
   
        lerpedColor = Color.Lerp(InFogColor, LastInFogColor, Time.time);
    }
}

Check these videos about more info how lerp works (that could be the problem)

http://unity3d.com/learn/tutorials/modules/beginner/live-training-archive/tips-tricks-4