Cutout + Specularmask-shader error: "Material doesn't have a color property"

I'm making a transparent coutout-shader that should also support a mask for speculartint. On compiling, Unity gives me the errors "Material doesn't have a ... property" for every value the shader has. I'm pretty new to shaders, so any help will be greatly appreciated :)

 Shader "Custom/Transparent_Cutout_Speculartint"
 {
     Properties
     {
         _Color ("Main Color", Color) = (1,1,1,1)
         _SpecColor ("Specular Color", Color) = (0.5, 0.5, 0.5, 1)
         _Shininess ("Shininess", Range (0.03, 1)) = 0.5
         _Cutoff("Cutoff", Range (0, 1)) = 0.5
 
         _MainTex ("Base (RGB) Trans (A)", 2D) = "white" {}
         _SpecTex ("Spec (RGB)", 2D) = "white" {}
     }
  
     SubShader
     {
         Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}
         LOD 400
  
         CGPROGRAM
         #pragma surface surf BlinnPhong alpha
  
         sampler2D _MainTex;
         sampler2D _SpecTex;
 
         half3 _Color;
         half3 _SpecColor;
 
         float _Shininess;
         float _Cutoff;
 
         struct Input 
         {
         float2 uv_MainTex;
         float2 uv_SpecTex;
         };
  
         void surf (Input IN, inout SurfaceOutput o)
         {
             fixed4 albedo = tex2D(_MainTex, IN.uv_MainTex) * _Color.rg;
             fixed4 specTex = tex2D(_SpecTex, IN.uv_SpecTex) * SpecColor.rgb;
 
             o.Albedo = albedo.rgb;
             o.Gloss = specTex.rgb;
             o.Specular = specTex.rgb;
 
             if (albedo.a > _Cutoff)
             o.Alpha = 1;
             else
             o.Alpha = 0;
 
         }
     ENDCG
     }
     Fallback "Transparent/VertexLit"
 }