added color override to unlabeled objects

com.unity.perception/Runtime/GroundTruth/RenderPasses/CrossPipelinePasses/LocalPositionCrossPipelinePass.cs

     class LocalPositionCrossPipelinePass : GroundTruthCrossPipelinePass
     {
         const string k_ShaderName = "Perception/LocalPosition";
+        static readonly int k_Override = Shader.PropertyToID("_Override");
         static readonly int k_Center = Shader.PropertyToID("_Center");
         static readonly int k_Size = Shader.PropertyToID("_Size");
 
             MaterialPropertyBlock mpb, Renderer renderer, Labeling labeling, uint instanceId)
         {
             var bounds = renderer.GetComponentInChildren<MeshFilter>().sharedMesh.bounds;
+            mpb.SetColor(k_Override, Color.white);
-        public override void ClearMaterialProperties(MaterialPropertyBlock mpb, Renderer renderer, Labeling labeling, uint instanceId)
+        public override void ClearMaterialProperties(
+            MaterialPropertyBlock mpb, Renderer renderer, Labeling labeling, uint instanceId)
-            // mpb.SetVector(k_Center, Color.black);
+            mpb.SetColor(k_Override, Color.black);
         }
     }
 }

com.unity.perception/Runtime/GroundTruth/Resources/LocalPosition.shader

     {
         _Center ("Center", Vector) = (0, 0, 0, 0)
         _Size ("Size", Vector) = (1, 1, 1, 0)
+        _Override ("Override", Color) = (0, 0, 0, 1)
     }
 
     HLSLINCLUDE
 
             float4 _Center;
             float4 _Size;
-            
+            fixed4 _Override;
+
             struct app_to_vertex
             {
                 float4 vertex : POSITION;
                 o.vertex = UnityObjectToClipPos(input.vertex);
                 o.vertex_object_space = (input.vertex - _Center) / _Size + float4(0.5, 0.5, 0.5, 1);
                 o.vertex_object_space.w = 1;
+                o.vertex_object_space = o.vertex_object_space * _Override;
                 return o;
             }