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)]; 
}

Like this. Just randomize the startColor