Mesh not working

I'm trying to make a mesh with a colours and different highs on it so that it resembles a landscape with mountains and lakes and so forth, but for some reason the mesh only appears as a black completely flat plane. I dont know why this is happening, so if anyone have any suggestions please help. Code for the mesh generator script.

 public static class MeshGenerator
 {
     public static MeshData GenerateTerrainMesh(float[,] heightMap, float heightMultiplier)
     {
         int width = heightMap.GetLength(0);
         int height = heightMap.GetLength(1);
         float topLeftX = (width - 1) / -2f;
         float topLeftZ = (height - 1) / 2f;
 
         MeshData meshData = new MeshData(width, height);
         int vertexIndex = 0;
 
         for (int y = 0; y < height; y++)
         {
             for (int x = 0; x < width; x++)
             {
                 meshData.vertices[vertexIndex] = new Vector3(topLeftX + x, heightMap[x, y] * heightMultiplier, topLeftZ - y);
                 meshData.uvs[vertexIndex] = new Vector2(x / (float)width, y / (float)height);
 
                 if (x < width - 1 && y < height - 1)
                 {
                     meshData.AddTriangle(vertexIndex, vertexIndex + width + 1, vertexIndex + width);
                     meshData.AddTriangle(vertexIndex + width + 1, vertexIndex, vertexIndex + 1);
                 }
 
                 vertexIndex++;
             }            
         }
 
         return meshData;
 
     }
 }
 
 public class MeshData
 {
     public Vector3[] vertices;
     public int[] triangles;
     public Vector2[] uvs;
 
     int triangleIndex;
 
     public MeshData(int meshWidth, int meshHeight)
     {
         vertices = new Vector3[meshWidth * meshHeight];
         uvs = new Vector2[meshWidth * meshHeight];
         triangles = new int[((meshWidth - 1) * (meshHeight - 1)*6)];
     }
 
     public void AddTriangle(int a, int b, int c)
     {
         triangles[triangleIndex] = a;
         triangles[triangleIndex+1] = b;
         triangles[triangleIndex+2] = c;
         triangleIndex += 3;
     }
 
     public Mesh CreateMesh()
     {
         Mesh mesh = new Mesh();
         mesh.vertices = vertices;
         mesh.triangles = triangles;
         mesh.uv = uvs;
         mesh.RecalculateNormals();
         return mesh;
     }
 }

Also I have this in another script.

         else if (drawMode == DrawMode.Mesh)
         {
             display.DrawMesh (MeshGenerator.GenerateTerrainMesh(noiseMap, meshHeightMultiplier), TextureGenerator.TextureFromColourMap(colourMap, mapWidth, mapHeight));
         }