Unity - Change cube color before placement - unity3d

Question

So, I am making a Minecraft-like game, and you basically move around on a pre-generated floor and place blocks. My problem is that I need to get the ability for the player to change the block color by hitting a numberpad key, ex: 1 for red, 2 for blue, and so on.
Here is the script that generates the floor, and handles block placement.
var range : float = Mathf.Infinity;
var hit : RaycastHit;
for (var y = -4; y < 50; ++y)
for (var x = -4; x < 50; ++x) {
var block : GameObject = GameObject.CreatePrimitive(PrimitiveType.Cube);
block.transform.position = transform.position + Vector3(x, -3, y);
}
function Update () {
if (Input.GetMouseButtonDown(0) && Hit()) {
var cube = GameObject.CreatePrimitive(PrimitiveType.Cube);
cube.transform.position = hit.transform.position + hit.normal;
}
if (Input.GetMouseButtonDown(1) && Hit())
Destroy(hit.transform.gameObject);
if (Input.GetKeyDown(KeyCode.Keypad1)) {
cube.renderer.material.color = Color.red;
}
if (Input.GetKeyDown(KeyCode.Keypad2)) {
cube.renderer.material.color = Color.blue;
}
if (Input.GetKeyDown(KeyCode.Keypad3)) {
cube.renderer.material.color = Color.yellow;
}
if (Input.GetKeyDown(KeyCode.Keypad4)) {
cube.renderer.material.color = Color.green;
}
if (Input.GetKeyDown(KeyCode.Keypad5)) {
cube.renderer.material.color = Color.magenta;
}
}
function Hit() : boolean {
return Physics.Raycast(transform.position, transform.forward, hit, range, 1);
}