Can I call a function on a behavior attached to a prefab from it's spawner object?

I am making a falling block game. The blocks can be red, orange, yellow, green, or blue. Besides just having different materials, each color has other properties I’ll need to implement later.

I also want it to be possible for other objects to change the color of each individual instance of Box later on. I’m not sure if this is formed correctly, but I don’t get any errors with this code:

public class BoxProperties : MonoBehaviour {

	public Material RedMat;
	public Material OrangeMat;
	public Material YellowMat;
	public Material GreenMat;
	public Material BlueMat;

	public enum BoxType {		Red, Orange, Yellow, Green, Blue	}

	public BoxType myType;

	////snipped Start() and Update()

	public void setType(BoxType newtype) {

		switch (newtype) {
			case BoxType.Red:
				renderer.material = RedMat;
			case BoxType.Orange:
				renderer.material = OrangeMat;
			case BoxType.Yellow:
				renderer.material = YellowMat;
			case BoxType.Green:
				renderer.material = GreenMat;
			case BoxType.Blue:
				renderer.material = BlueMat;

		myType = newtype;

I made setType() public so other objects can use it to change the type of any given instance.

Additionally, I have a non-renderable cube that represents a spawn volume. I am able to get the Box instances to spawn at random points in the cube and fall, but I am not sure how I can get at the prefab instance’s setType method to set the type of box after spawning.

public class SpawnBoxes : MonoBehaviour {
	private Vector3 nextpos;	//Randomly picked new spawn position
	private float collecttime;	//Counts how long has passed since the last spawn
	private GameObject nextbox;

	public float spawntime;
	public GameObject spawnee;	//Box object goes here

	// Use this for initialization
	void Start () {
		collecttime = 0;
	// Update is called once per frame
	void Update () {
		collecttime += Time.deltaTime;

		if (collecttime > spawntime) {
			nextpos = randPos(renderer.bounds.size, transform.position);
			collecttime = 0;
			nextbox = Instantiate(spawnee,nextpos,Random.rotation) as GameObject;
			//Set type of nextbox, not sure how to access that function, but it's part of a component script attached to the Box prefab
			nextbox.GetComponent("BoxProperties").setType(BoxType.Green); //Doesn't work.
//snipped randPos()


I realize there are some other approaches, like making separate prefabs for each Box type and spawning one randomly, but I wonder if there is a way to make this call work?

SomeScriptName someScript = someGameObject.GetComponent();