Vertex colors not working in shader graph.

I made a simple test triangles and created a shader graph with vertex color connected to the albedo of the pbr master. Instead of the intended red color, it is only gray, as if the vertex color did not exist.

 void Start()
 {
     Vector3[] verticies;
     int[] triangles;
     Color[] colors;

     verticies = new Vector3[3];
     triangles = new int[3];
     colors = new Color[3];

     verticies[0] = new Vector3(0.0f, 0.0f, 0.0f);
     verticies[1] = new Vector3(1.0f, 0.0f, 0.0f);
     verticies[2] = new Vector3(0.5f, 1.0f, 0.0f);

     triangles[0] = 0;
     triangles[1] = 1;
     triangles[2] = 2;

     for(int i = 0; i < colors.Length; i++)
     {
         colors[i] = Color.red;
     }

     Mesh mesh = GetComponent<MeshFilter>().mesh;

     mesh.vertices = verticies;
     mesh.triangles = triangles;
     mesh.colors = colors;
 }