Random enemy color

I have a function randomly spawning 15 enemies, with random scale and now Im trying to assign a random color for each of them.

void Start()
	{
		mat = GetComponent<Material> ();
		for (int i = 0; i < 15; i++)
		{
			float s = Random.Range (1F,15F);                                                                                                                        //size

			Vector3 position = new Vector3(Random.Range(-100.0F, 100.0F),Random.Range(-100.0F, 100.0F), Random.Range(-100.0F, 100.0F));//position
			Instantiate(prefab, position, Quaternion.identity);
			prefab.transform.localScale = new Vector3(s,s,s);

				randomNumber = Random.Range(1,3);                                                                                               //material
                                


						switch (randomNumber)
                                {
                                        case 1:
												GetComponent<Renderer>().material.color = Color.yellow;
                                                break;
                                        case 2:
												GetComponent<Renderer>().material.color = Color.blue;     
                                                break;
                                        case 3:
												GetComponent<Renderer>().material.color = Color.green;     
                                                break;
                                }      
                               
                               

			
			
		}
		
		
	}

This function changes the color of player. How to change it to assign randomly to enemy?

First: Don’t change the prefabs scale. Change the enemy clones scale.

Instantiate(prefab, position, Quaternion.identity);
prefab.transform.localScale = new Vector3(s,s,s); // Please don't mess with the prefab

Change it to this:

GameObject enemy = (GameObject) Instantiate(prefab, position, Quaternion.identity);
enemy.transform.localScale = new Vector3(s,s,s);

Ok, so you want to change the color of the enemy, so get the renderer of the enemy.

Renderer enemyRenderer = enemy.GetComponent<Renderer>();

Then you can just set the color to something

enemyRenderer.material.color = Color.red;