Change color of multiple game objects in Unity 5

Question

I would like to change the color of multiple gameobjects in Unity using a single script. I'm kinda lost in the way how to do it. I'm new to Unity and this is some sort of basic training for me.

Unity version: 5.3.4

Observed Behavior:

Added the same script to the other gameobjects and all change to the same color

Expected Behavior:

Change the color of the gameobjects individually

List of things tried:

Using the -FindGameObject-

Tried to acces the materials using the -GameObject-

Tried both at the same time

Thinking in multiple scripts to achieve the results I want

Here's the code

C#:

using UnityEngine;
using System.Collections;

public class ChangeColor : MonoBehaviour 
{
   //If I change these variables to -GameObject-
   //It blocks me to access the renderer
   //Making the variables public doesn't work either
   private Renderer cube;
   private Renderer sphere;

void Start () 
{
    //Tried here the -FindGameObjectWithTag-
    cube = GetComponent<Renderer>();
    sphere = GetComponent<Renderer>();
}

void Update () 
{
    if(Input.GetKeyDown(KeyCode.A))
    {
        //Tried here the -FindGameObjectWithTag-
        cube.material.color = Color.red;
    }

    if(Input.GetKeyDown(KeyCode.S))
    {
        //Tried here the -FindGameObjectWithTag-
        sphere.material.color = Color.green;
    }
  }
}

Maybe I'm doing something wrong, as I said I'm new to Unity, I kindly accept any help, if it is noobfriendly the better.

Thanks

Answer 1

There are a couple different ways you can go about doing this.

1. If they are all under the same parent without other objects there too you could loop through the children and change their colors

   GameObject Parent = GameObject.Find("ParentObject");
   for( int x = 0; x > Parent.transform.childCount; x++);
   {
     Parent.transform.GetChild(x).GetComponent<Renderer>().material.color = Color.red;
   }
   

2. If there are less than say 20ish, you could create a list and simply drag and drop each transform into the inspector after changing the list's size to the number of objects you have.

   /*Make sure you have Using "System.Collections.Generic" at the top */
   //put this outside function so that the inspector can see it
   public List<Transform> Objs;
   // in your function put this (when changing the color)
   foreach(Transform Tform in Objs){
     Tform.GetComponent<Renderer>().material.color = Color.red;
   }
   

3. Similarly to 2, if you want to do it all in code you can do

   //Outside function
   public List<Transform> Objs;
   //inside function
   Objs.Add(GameObject.Find("FirstObject").transform);
   Objs.Add(GameObject.Find("SecondObject").transform);
   //... keep doing this
   //now do the same foreach loop as in 2
   

4. You could search by tag (if you have a lot of objects) (i would imagine that this would take a bit longer just because it is going through each component but I have no evidence to back that up)

   //Outside function
   public GameObject[] Objs;
   //inside function
   Objs = GameObject.FindGameObjectsWithTag("ATagToChangeColor");
   
   foreach(Transform Tform in Objs){
     Tform.GetComponent<Renderer>().material.color = Color.red();
   }
   

And about this comment:

//If I change these variables to -GameObject-
//It blocks me to access the renderer
//Making the variables public doesn't work either

If you make them of type GameObject then you should easily be able to access the renderer simply by doing this:

public GameObject cube;
public void Start(){
    cube.GetComponent<Renderer>().material.color = Color.red();
}

And making the variables public allows unity's inspector to see the variables so that you can change them in the unity editor without having to open the script.