Grayscale Shader

Shader.shader

Shader "Custom/Grey Texture" {

  Properties {
        _MainTex ("Base (RGB) Trans (A)", 2D) = "white" {}
    }

    SubShader {
        Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}
        LOD 200

        CGPROGRAM
        #pragma surface surf Lambert alpha

            sampler2D _MainTex;

            struct Input {
                float2 uv_MainTex;
            };

            void surf (Input IN, inout SurfaceOutput o) {
                half4 c = tex2D(_MainTex, IN.uv_MainTex);
                o.Albedo = dot(c.rgb, float3(0.3, 0.59, 0.11));
                o.Alpha = c.a;
            }

        ENDCG
    }

}