Sprite Color.Lerp

I don't know why this code is making my sprite disappear?

 using UnityEngine;
 using System.Collections;
 
 public class ObetacleColor : MonoBehaviour {
 
 
     private SpriteRenderer spriterenderer;
     private float ltime = 0;
     public float ltimespeed;
     int count = 1;
     
     public Color one;
     public Color two;
     public Color three;
     
     
     
     // Use this for initialization
     void Start () {
 
         spriterenderer = GetComponent<SpriteRenderer>();
         //Invoke("One", 1f);
         
     }
     
     void One(){
         
     spriterenderer.color = Color.Lerp(one, two, ltime);
         
         
     }
     
     void Two (){
         
         spriterenderer.color = Color.Lerp(two, three, ltime);
         
     }
     
     void Three (){
         
         spriterenderer.color = Color.Lerp(three, one, ltime);
         
     }
     
     // Update is called once per frame
     void Update () {
         
         
         if (ltime < 1){
             ltime += .01f / ltimespeed;
         }
 
         //spriterenderer.color = Color.Lerp(one, two, Mathf.PingPong( Time.time, 5));
 
         if (ltime >= 1){
             
             count++;
             if (count == 1){
                 
                 Invoke("One", 1f);
                 
             }
             if (count == 2){
                 
                 Invoke("Two", 1f);
             }
             if (count == 3){
                 
                 Invoke("Three", 1f);
             }
             ltime = 0;
             
         }
         
         if (count == 4){
             
             count = 1;
             
         }
         
 
         
         
         
     }
 }