If my question was a bit vague i'll expand here;

Basically what i want to do is have a little icon of a stomach (To represent hunger) and every frame have a variable that contains the hunger decrease by 0.1. Once the hunger level reaches certain intervals, i want the color to change on the guiTexure, for example; at 500.0f color = yellow at 250.0f color = red

I'm fairly new to scripting in unity, so i could be way off with this code, so can somebody please help me

It will decrease the CurrentHunger variable, however the colors do not change at the intervals.

Here's my code;

using UnityEngine;
using System.Collections;

public class Hunger : MonoBehaviour 
{
    public float CurrentHunger = 1000.0f;
    public float MaxHunger = 1000.0f;
    // Use this for initialization
    void Start () 
    {

    }

    // Update is called once per frame
    void Update () 
    {
       CurrentHunger -= 0.1f;

    if (CurrentHunger > MaxHunger)
       {
         CurrentHunger = MaxHunger;
       }
    }
    void OnGui ()
    {
       if (CurrentHunger == 500.0f)
       {
         guiTexture.color =  Color.yellow;
       }
    else if (CurrentHunger == 250.0f)
       {
         guiTexture.color =  Color.red;
       }
    }
}