How ca i change to random light color smoothly?

I wrote a script to change color to a random color, but it changes intantly to the new color. How can i make that it changes smoothly to the new color?

 var colors : Color[];
 var light : Light;
 
 function LightColorChange () 
 {
     light.color = colors[Random.Range(0,colors.Length)]; 
 }