Shader that uses Vertex Colors and Renders some as Transparent

Hello everyone,

I was looking to see if I could get some help on a problem I've been spending a while trying to solve. I have an imported .fbx mesh that's colored by vertex colors.

Here's a screenshot of the mesh I'm using. https://imgur.com/a/FY8Z38r

Here's the shader I'm using on that GameObject's material.

Shader "Custom/VertexColor" { // Where it will appear inside of the Shader Dropdown Menu of the Material / Name of the shader

SubShader{
Tags { "RenderType" = "Opaque" }
LOD 200


CGPROGRAM
#pragma surface surf Lambert vertex:vert
#pragma target 3.0

struct Input {
float4 vertColor;
};

float _CutoutThresh;

void vert(inout appdata_full v, out Input o) {
UNITY_INITIALIZE_OUTPUT(Input, o);
o.vertColor = v.color;
}

void surf(Input IN, inout SurfaceOutput o) {

#include "UnityCG.cginc

o.Albedo = IN.vertColor.rgb;
clip(IN.vertColor.r = 0.3); // Discards any pixel whose interpolated vertex color in the red channel is less than 0.5
}
ENDCG
}
FallBack "Diffuse"
}

I want to be able to make all blue parts of the mesh render as transparent. However, the shader above doesn't work, even though I think it should. Does anyone have any ideas?

 

wtf?