Get Component Light problem

I am creating a system that the player must click on a sequence of buttons to turn on a machine. Each time he clicks a button, plays an animation of the object and one light is lit. The problem is that the second time on the player passes through the button, the program warns that cannot add other component. Any way to fix it? Thanks.

    var a = false;
	var b = false;
	var c = false;

		if (hit.gameObject.tag == "bt1" && a == false) {
		a = true;
		var bhit1 : GameObject = GameObject.FindWithTag("bt1");
		bhit1.animation.Play ("anim1");
    	if (hit.gameObject.tag == "bt2" && b == false) {
		b = true;
		var bhit2 : GameObject = GameObject.FindWithTag("bt2");
		bhit2.animation.Play ("anim2");
		if (hit.gameObject.tag == "bt3" && c == false) {
		c = true;
		var bhit3 : GameObject = GameObject.FindWithTag("bt3");
		bhit3.animation.Play ("anim3");

Rather than add and remove components (you don’t show the code where you remove the Lights, but I suspect that is your problem) why not just have a light on each of your buttons and change the intensity of the light?