Reding from Mesh.colors doesn't display vertex colors of fbx

I have an exported fbx with different vertex colors on it.

This script runs on start:

 function Start () {
     var mesh : Mesh = GetComponent(MeshFilter).mesh;
     var vertices : Vector3[] = mesh.vertices;
     var colors : Color[] = new Color[vertices.Length];
     
     for (var i = 0; i < vertices.Length;i++)
     {
         Debug.Log(colors[i]);
     }
 }

For some reason the readout is RGBA(0.00, 0.00, 0.00, 0.00) for every vertice, even though many of them should have differing values from this.

Anyone encountered this before?