How to find the most present color in an image ?

Hello everyone, i'm trying to find the most present color in an image. My program is scanning all the pixels of an image and I wish it returns me the color that is the most present in the image. I have no apparent error, but when I run the program, unity seems to freeze or loop forever.
The problem is inside Colors.cs and within the function "MainColorFromTexture"
Can anyone help me please ?



EDIT:
Ok, i found the problem. This code is just not optimized at all. It runs correctly, but is just really slow with big pictures. The more colors there are and the more pixels there are inside the picture, and the more it will take time to complete. Sounds obvious said like that, but i didn't expect this code to be this slow.

The slow loop is inside colors.cs line 32.

Anyone could give me hints to optimize this ?


Here is my code :

DrawColor.cs

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class DrawColor : MonoBehaviour
 {
     [SerializeField] private Texture2D tex2d;
     [SerializeField] private RawImage rImg;
     [SerializeField] private Colors co;
 
     private Color32 col;
 
     void Start()
     {
         //col = co.AverageColorFromTexture(tex2d);
         col = co.MainColorFromTexture(tex2d);
         rImg.color = col;
     }
 }

Colors.cs

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Colors : MonoBehaviour
 {
     public Color32 AverageColorFromTexture(Texture2D tex)
     {
         Color32[] texColors = tex.GetPixels32();
         int total = texColors.Length;
         float r = 0;
         float g = 0;
         float b = 0;
 
         for (int i = 0; i < total; i++)
         {
             r += texColors[i].r;
             g += texColors[i].g;
             b += texColors[i].b;
         }
 
         return new Color32((byte)(r / total), (byte)(g / total), (byte)(b / total), 255);
     }
 
 
     public Color32 MainColorFromTexture(Texture2D tex)
     {
         Color32[] texColors = tex.GetPixels32();
         int total = texColors.Length;
         List<colNum> colNumList = new List<colNum>();
 
         for (int i = 0; i < total; i++)
         {
             if (colNumList.Count > 0)
             {
                 for (int j = 0; j < colNumList.Count; j++)
                 {
                     if (colNumList[j].col.Equals(texColors[i])) colNumList[j].quantity += 1;
                     else AddColNumToList(texColors[i], colNumList);
                 }
             }
             else AddColNumToList(texColors[i], colNumList);
         }
 
         Color32 col = new Color32();
         int quan = 0;
 
         foreach(colNum cn in colNumList)
         {
             if (cn.quantity > quan)
             {
                 col = cn.col;
                 quan = cn.quantity;
             }
         }
 
         col.a = 255;
 
         return col;
 
     }
 
     private void AddColNumToList(Color32 col, List<colNum> li)
     {
         colNum cn = new colNum();
         cn.col = col;
         cn.quantity = 1;
         li.Add(cn);
     }
 }
 
 public class colNum
 {
     public Color32 col;
     public int quantity;
 }