How would I make the text bigger on this script?

How would I make the text bigger on this script. I’ve been trying to change it, but if I do it messes with the point system. Thank you!
using UnityEngine;
using System.Collections;

public class ScoreManager : MonoBehaviour {
	public int score = 0;

	void OnGUI() {
		GUI.color = Color.black;
		GUI.Label( new Rect(0,0, 100, 50), "Score: " + score);
	}

}

use a class called GUIStyle

GUIStyle style = new GUIStyle() ;
style.fontSize = 30; // <--- change Font Size Here
GUI.Label( new Rect(0,0, 100, 50), "Score: " + score, style);