All Arrayinstances get changed

Hello, i am new here and i hope that somebody can help me with my problem. I am trying to create a script, which creates a mesh out of information from a textfile in a voxel design (the voxeleditor i use saves its models in a simple text format ^^)

For this task i did create my own Variabletype I called "Voxel", which simple saves a color as Vector3 and information about the shown faces/sides as a int-array (simply: is a side drawn (=1) or not drawn (=0)). Now i do have the problem that, when ever i set one face of one Voxelinstance to 1, all other instances of Voxel also get that value changed to 1. In the beginning i used "struct" and not "class" for the "Voxel"-Script, but i changed it just for checking if that was the fault. I hope i described everything cleary enough and that somebody has got a simple solution for me. Greetings, Firedra.

Voxel class:

    using UnityEngine;
     using System.Collections;
     [System.Serializable]
     public class Voxel{
         private Vector3 color;
         public int[] face;
         public Voxel (Vector3 c, int[] f)
         {
             color = new Vector3();
             face = new int[6];
             if (f.Length == 6){
                 color = c;
                 face = f;
             }
         }
         public void SetColor(Vector3 newColor)
         {
             color = newColor;
         }
         // Faceindendifier
         // 0 = Front
         // 1 = Back
         // 2 = Down
         // 3 = Up
         // 4 = Left
         // 5 = Right
         public void SetFace(int index)
         {
             this.face[index] = 1;
         }
         public void RemoveFace(int index)
         {
             this.face[index] = 0;
         }
         public Vector3 GetColor()
         {
             return color;
         }
         public int GetFace(int index)
         {
             return face[index];
         }
     }

Test Script to show the state of a face via GUI for 6 Voxelinstances.

 using UnityEngine;
 using System.Collections;
 
 public class _DebugVoxelFace : MonoBehaviour {
     public Voxel[] blocks;
     
     // Use this for initialization
     void Start () {
         blocks = new Voxel[6];
         int[] f = new int[6];
         f[0] = 0;
         f[1] = 0;
         f[2] = 0;
         f[3] = 0;
         f[4] = 0;
         f[5] = 0;
         blocks[0] = new Voxel(new Vector3(1,0,0),f);
         blocks[1] = new Voxel(new Vector3(2,0,0),f);
         blocks[2] = new Voxel(new Vector3(3,0,0),f);
         blocks[3] = new Voxel(new Vector3(4,0,0),f);
         blocks[4] = new Voxel(new Vector3(5,0,0),f);
         blocks[5] = new Voxel(new Vector3(6,0,0),f);
     }
     void OnGUI(){
         for(int i = 0; i < 6; i++){
             string s = blocks[i].GetFace(0).ToString();
             if (GUI.Button(new Rect(200+80*i,200,70,50),s)){
                 if (blocks[i].GetFace(0)==0) blocks[i].SetFace(0);
                 else blocks[i].RemoveFace(0);
             }
         }
     }
 }