Fade out GUI Texture on android

I want to make a gui texture fade out after 1.5 seconds. For that purpose I wrote this code:

using UnityEngine; using System.Collections;

public class alphaScript : MonoBehaviour { private float flag;

 void Start()
 {
     flag = 0;
 }
 
 void OnGUI()
 {
     if(flag > 1.5)
     {
         Color textureColor = guiTexture.color;
         textureColor.a -= Time.deltaTime / 2;
         guiTexture.color = textureColor;
     }
 }
 void Update()
 {
     flag += Time.deltaTime;
 }

}

This script works perfectly on Windows but for some reason this texture don't even come up on android. What did I do wrong? Thanks in advance.