Change object texture

I'm currently trying to edit some code to see if an object in an array has a higher x value than 4 in distance between itself and its previous member. From my code I know that it happens but the texture doesn't change. Any help?

Code (csharp):

1.  
2. public Texture tester;
3.  
4. for(int i = 0; i < arrayLength.Length; i++)
5.         {              
6.             if(arrayLength.Length-1 != null)
7.             {              
8.                 transform.position = new Vector3(spawnPosX + random_x * LengthRadius, spawnPosY + random_y * HeightRadius+1.2f, spawnPosZ  + random_z * LengthRadius);
9.             }
10.            
11.             platSpwans = arrayLength[i].transform.position;
12.                
13.             arrayLength[i].transform.position = new Vector3(platSpwans.x + random_x * LengthRadius, platSpwans.y + random_y * HeightRadius+1.25f, platSpwans.z  + random_z * LengthRadius);
14.            
15.             if (i > 1)
16.             {
17.            
18.                 if (arrayLength[i].transform.position.x > (arrayLength[i -1].transform.position.x+4))
19.                 {
20.                     arrayLength[i].renderer.material.SetTexture("test", tester );
21.                     Debug.Log("true");
22.                 }
23.             }

 

I assume arraylength is gameobjects?

I would use .GetComponent(Renderer) and place that in the variable like rend

Then go rend.material = the new material and make a different material for each of the changes you want.