Animating the Color.a on a Vertex Color Shader for iPhone

I wrote a script to change the alpha of a Vertex Color shader. It works fine in the editor, but doesn't fade to transparent on the iPhone (3Gs). I'm not sure if this is a technical limitation of the phone, or if I don't understand what I am doing again. Thanks in advance.

void Update(){
      Color thisColor = textGO.GetComponent<MeshRenderer>().material.color;
      thisColor.a -= .0025f;
      textGO.GetComponent<MeshRenderer>().material.color = thisColor;
}

I am not sure why it has started to work, but it seems fine now. I do realize I can access the GameObject this way instead:

textGO.renderer.material.color;

But it still is working the other way too.

Strange.

untested code:

using UnityEngine;
using System.Collections;

public class FadeAway : MonoBehaviour {
	
	public float targetAlphaValue = 0.0f; // target alpha value 0.0f to 1.0f
	public float fadeTime = 1.75f; // time to fade to target alpha value
	private Color startColor;
	private Color targetColor;
	private Color lerpedColor;
	private Material objMaterial;
	
	// Use this for initialization
	void Start () {
		objMaterial = gameObject.renderer.material;
		startColor = objMaterial.color;
		targetColor = new Color(startColor.r,startColor.g,startColor.b,targetAlphaValue);
		
	}
	
	// Update is called once per frame
	void Update () {
		lerpedColor = Color.Lerp(startColor, targetColor, fadeTime);
		objMaterial.color = lerpedColor;
	}
	
	void ResetColor(){
		objMaterial.color = startColor;
	}
}