i want to build a function for a debuger i am working on,for this i want to make a grid 24*32 on the screen and show me in which square the mouse is at every point of time i want to color red the square. in order to do it i created a plane with a material red.png i set the alpha to 0. next i want that when my mouse is on the square to set the alpha of the square to 1 and restore to 0 if i leave the square.

my questions a) is there a better way to do it? b) what i did ,didnt work can anyone help me figuring out why?

thanks in advance and sorry for the poor english

using UnityEngine;
using System.Collections;

public class Bitmap : MonoBehaviour {

public  int Columns=32,Rows=24;
public int MouseCol,MouseRow;
 bool[] IsSquareColored;

    Texture2D texture;
    // Use this for initialization
    void Start () {

    IsSquareColored= new bool[Columns*Rows];



       texture=(Texture2D) this.transform.gameObject.renderer.sharedMaterial.mainTexture;
    }

    // Update is called once per frame
    void Update () {


       Vector2 MousePos= Input.mousePosition;    
       MouseCol= (int)(MousePos.x * Columns / Screen.width);
     MouseRow = (int)(MousePos.y *Rows /Screen.height);
    MouseCol=  Mathf.Clamp(MouseCol,0,Columns);
    MouseRow=  Mathf.Clamp(MouseRow,0,Rows);

    // Paint red

    for (int i=0;i<Rows;i++)
       {
         for ( int j=0;j<Columns;j++)
         {
          if (!IsSquareColored[ (MouseRow-1)*(Columns)+MouseCol] && (MouseCol==j )&& (MouseRow==i)){
              Paint(MouseRow,MouseCol);  
          }
          else  if (IsSquareColored[ (MouseRow-1)*(Columns)+MouseCol] && ((MouseCol!=j ) || (MouseRow!=i))){
              Unpaint(i,j);
          }
         }
       }

    }

    void Paint(int R,int C)
    {

       Color32[] colors= texture.GetPixels32();
       for (int i = (R*Screen.height/Rows);i<((R+1)*Screen.height/Rows);i++)
         for  (int j = (C*Screen.width /Columns);j<((C+1)*Screen.width /Columns);j++)
         colors[i*Screen.width+j].a=1;










    }
    void Unpaint(int R,int C){}

}