Created a shader that can remove the background of the segmentation image

com.unity.perception/Runtime/GroundTruth/Labelers/Resources/SegRemoveBackgroundShader.shader

+Shader "Unlit/SegRemoveBackgroundShader"
+{
+    Properties
+    {
+        _BaseMap ("Base (RGB) Trans (A)", 2D) = "white" { }
+        _RemoveColor ("Remove Color", Color) = (0, 0, 0, 1)
+        _SegmentTransparency("Segment Transparency", Range(0.0,1.0)) = 0.5
+        _BackTransparency("Background Transparency", Range(0.0,1.0)) = 0
+    }
+    SubShader
+    {
+        Tags { "Queue"="Transparent" "RenderType"="Transparent" }
+        LOD 100
+
+        ZWrite off
+        Blend SrcAlpha OneMinusSrcAlpha
+
+        Pass
+        {
+            CGPROGRAM
+            #pragma vertex vert
+            #pragma fragment frag Lambert alpha
+ 
+            #include "UnityCG.cginc"
+
+            struct appdata
+            {
+                float4 vertex : POSITION;
+                float2 uv : TEXCOORD0;
+            };
+
+            struct v2f
+            {
+                float2 uv : TEXCOORD0;
+                float4 vertex : SV_POSITION;
+            };
+
+            sampler2D _BaseMap;
+            fixed4 _RemoveColor;
+            float _SegmentTransparency;
+            float _BackTransparency;
+
+            v2f vert (appdata v)
+            {
+                v2f o;
+                o.vertex = UnityObjectToClipPos(v.vertex);
+                //o.uv = TRANSFORM_TEX(v.uv, _MainTex);
+                o.uv = v.uv;
+                return o;
+            }
+
+            fixed4 frag (v2f i) : SV_Target
+            {
+                // sample the texture
+                fixed4 col = tex2D(_BaseMap, i.uv);
+                
+                if (abs(col.r - _RemoveColor.r) < .01f)
+                {
+                    if (abs(col.g - _RemoveColor.g) < .01f)
+                    {
+                        if (abs(col.b - _RemoveColor.b) < .01f)
+                        {
+                            col.a = _BackTransparency;
+                        }
+                    }
+                }
+                
+                if (abs(col.a - _BackTransparency) > .01f) col.a = _SegmentTransparency;
+
+                return col;
+            }
+            ENDCG
+        }
+    }
+}

com.unity.perception/Runtime/GroundTruth/Labelers/Resources/SegRemoveBackgroundShader.shader.meta

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