Setting Random Material color to game object inside unity editor

MaterialColor.cs

var newObstacle = Instantiate(cube, new Vector3(i, 0, j), Quaternion.identity, transform);
Renderer obstacleRenderer = newObstacle.GetComponent<Renderer>();

Material mat = new Material(obstacleRenderer.sharedMaterial);
mat.color = GetRandomColor();
obstacleRenderer.sharedMaterial = mat;


//
public Color GetRandomColor()
{
    var random = Random.Range(1, 10);

    if(random<4) return Color.red; 
    else if(random<7) return Color.blue; 
    else return Color.green; 
}