public GameObject gameObject;

//gameObject.GetComponent().material.color = new Color(r, g, b, a);
//gameObject.GetComponent().material.color = new Color(255.0f, 255.0f, 255.0f, 0.0f);
gameObject.GetComponent().material.color = new Color(255.0f, 255.0f, 255.0f, 100.0f);