Cg semitransparent colors based on alpha

Shader "Custom/Cg semitransparent colors based on alpha" {
Properties {
_MainTex ("RGBA Texture Image", 2D) = "white" {}
}
SubShader {
Tags {"Queue" = "Transparent"}

Pass {
Cull Front // first render the back faces
ZWrite Off // don't write to depth buffer
// in order not to occlude other objects
Blend SrcAlpha OneMinusSrcAlpha
// blend based on the fragment's alpha value

CGPROGRAM

#pragma vertex vert
#pragma fragment frag

uniform sampler2D _MainTex;
uniform float _Cutoff;

struct vertexInput {
float4 vertex : POSITION;
float4 texcoord : TEXCOORD0;
};
struct vertexOutput {
float4 pos : SV_POSITION;
float4 tex : TEXCOORD0;
};

vertexOutput vert(vertexInput input)
{
vertexOutput output;

output.tex = input.texcoord;
output.pos = mul(UNITY_MATRIX_MVP, input.vertex);
return output;
}

float4 frag(vertexOutput input) : COLOR
{
float4 color =  tex2D(_MainTex, input.tex.xy);
if (color.a > 0.5) // opaque back face?
{
color = float4(0.0, 0.0, 0.2, 1.0);
// opaque dark blue
}
else // transparent back face?
{
color = float4(0.0, 0.0, 1.0, 0.3);
// semitransparent green
}
return color;
}

ENDCG
}

Pass {
Cull Back // now render the front faces
ZWrite Off // don't write to depth buffer
// in order not to occlude other objects
Blend SrcAlpha OneMinusSrcAlpha
// blend based on the fragment's alpha value

CGPROGRAM

#pragma vertex vert
#pragma fragment frag

uniform sampler2D _MainTex;
uniform float _Cutoff;

struct vertexInput {
float4 vertex : POSITION;
float4 texcoord : TEXCOORD0;
};
struct vertexOutput {
float4 pos : SV_POSITION;
float4 tex : TEXCOORD0;
};

vertexOutput vert(vertexInput input)
{
vertexOutput output;

output.tex = input.texcoord;
output.pos = mul(UNITY_MATRIX_MVP, input.vertex);
return output;
}

float4 frag(vertexOutput input) : COLOR
{
float4 color = tex2D(_MainTex, input.tex.xy);
if (color.a > 0.5) // opaque front face?
{
color = float4(0.0, 1.0, 0.0, 1.0);
// opaque green
}
else // transparent front face
{
color = float4(0.0, 0.0, 1.0, 0.3);
// semitransparent dark blue
}
return color;
}

ENDCG
}
}
Fallback "Unlit/Transparent"
}