Creating a mesh for an overview map

I am generating a 2d procedurally generated map, and I would like to create a map to display an overview of said map. As i know it will be slow to have a game object on the overview map for every single tile in the world, I have decided to use a mesh. Having never used meshes before I am running into some trouble.

I have a meshFilter like so:

 private MeshFilter meshFilt;
 meshFilt = GetComponent<MeshFilter>();

and I am then trying to set the vertices of the mesh to the locations of the tiles:

  mesh = meshFilt.mesh;
     Vector3[] keys = revealedTiles.Keys.ToArray<Vector3>();
     mesh.vertices = keys;
     Color[] colors = new Color[mesh.vertices.Length];
     Random r = new Random();
     for (int i = 0; i < keys.Length; i++)
     {
         colors[i] = new Color(Random.Range(0.0f, 1.0f), Random.Range(0.0f, 1.0f), Random.Range(0.0f, 1.0f));
 
     }
     mesh.colors = colors;

Where keys is an array of Vector 3's, which are part of a dictionary. So basically what I am doing is setting the vertices of the mesh to an array of vector3's that represent the map coordinates of every tile (1,1 1,2 2,5 .etc).

Currently I am just setting the colors to a random color, just as a proof of concept.

However, the issue is that this does not seem to display anything. In the unity scene view I am getting an outline of a box that appears to be the right size, but it has nothing within it. In the game view nothing appears. I have checked that this code is running, and all of the vertices are being set properly. Any and all help is appreciated, and if anyone has a better idea on how to do this, I am more than willing to listen.

Thank you.

Edit: Here is a view of the scene view: