How can i make my game object not clickable?

i have this script where i click on my cubes and they turn to their respective color, but i can also change to the ball color and i dont want that. is there a way to make my ball unclickable? i've tried this so far but no success

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using UnityEngine.EventSystems;
5.  
6. public class ChangeBallColor : MonoBehaviour
7. {
8.     [SerializeField] GameObject ball;
9.     [SerializeField] Material ballMaterial;
10.     [SerializeField] Material cubeMaterial;
11.  
12.     // Start is called before the first frame update
13.     void Start()
14.     {
15.         Debug.Log(FindObjectOfType<ChangeBallColor>().gameObject);
16.     }
17.  
18.     // Update is called once per frame
19.     void Update()
20.     {
21.        
22.     }
23.  
24.     private void OnMouseDown()
25.     {
26.         if (EventSystem.current.IsPointerOverGameObject() == false)
27.         {
28.             ballMaterial.color = cubeMaterial.color;
29.         }
30.  
31.         if(ball)
32.         {
33.             return;
34.         }
35.     }
36. }
37.  

 

You could use tags or some other way to detect the object type you want to interact with.
And if you have a script that reacts to mouse clicks, don't add it to the ball?