######説明
マテリアルでEnableGPUInstancingにチェックを入れて使います。
Shader "Custom/Instancing"
{
    Properties
    {
        _MainTex("Albedo (RGB)", 2D) = "white"{ }  
    }
        SubShader
        {
            Tags { "RenderType" = "Opaque" }
            LOD 200

            CGPROGRAM
            #pragma surface surf Standard fullforwardshadows
            #pragma target 3.0

            sampler2D _MainTex;
            
            struct Input
            {
                float2 uv_MainTex;
            };
 
            UNITY_INSTANCING_BUFFER_START(Props)
            UNITY_DEFINE_INSTANCED_PROP(fixed4, _Color)
            UNITY_INSTANCING_BUFFER_END(Props)

            void surf(Input IN, inout SurfaceOutputStandard o)
            {
                fixed4 c = tex2D(_MainTex, IN.uv_MainTex) * UNITY_ACCESS_INSTANCED_PROP(Props, _Color);
                o.Albedo = c.rgb;
                o.Alpha = c.a;
            }
            ENDCG
        }
    FallBack "Diffuse"
}