Color replace shader

// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

Shader "Custom/Sprite Color Swap"
{
    Properties
    {
        _MainTex("Sprite", 2D) = "white" {}
        _Color("Color", Color) = (1,0,1,1)
        _IgnoreColorA("Ignore Color A", Color) = (1,0,1,1)
        _IgnoreColorB("Ignore Color B", Color) = (1,0,1,1)
        _IgnoreColorC("Ignore Color C", Color) = (1,0,1,1)
    }
    SubShader
    {
        Tags
        {
            "RenderType" = "Opaque"
            "Queue" = "Transparent+1"
        }

        Pass
        {
        ZWrite Off
        Blend SrcAlpha OneMinusSrcAlpha

        CGPROGRAM
        #pragma vertex vert
        #pragma fragment frag
        #pragma multi_compile DUMMY PIXELSNAP_ON

        sampler2D _MainTex;
        float4 _Color;
        float4 _IgnoreColorA;
        float4 _IgnoreColorB;
        float4 _IgnoreColorC;

        struct Vertex
        {
            float4 vertex : POSITION;
            float2 uv_MainTex : TEXCOORD0;
            float2 uv2 : TEXCOORD1;
        };

        struct Fragment
        {
            float4 vertex : POSITION;
            float2 uv_MainTex : TEXCOORD0;
            float2 uv2 : TEXCOORD1;
        };

        Fragment vert(Vertex v)
        {
            Fragment o;

            o.vertex = UnityObjectToClipPos(v.vertex);
            o.uv_MainTex = v.uv_MainTex;
            o.uv2 = v.uv2;

            return o;
        }

        float4 frag(Fragment IN) : COLOR
        {
            half4 c = tex2D(_MainTex, IN.uv_MainTex);

            if (c.r == _IgnoreColorA.r && c.g == _IgnoreColorA.g && c.b == _IgnoreColorA.b)
            {
                return c;
            }
            else if (c.r == _IgnoreColorB.r && c.g == _IgnoreColorB.g && c.b == _IgnoreColorB.b)
            {
                return c;
            }
            else if (c.r == _IgnoreColorC.r && c.g == _IgnoreColorC.g && c.b == _IgnoreColorC.b)
            {
                return c;
            }
            else if (c.a == 0)
            {
                return c;
            }
            else
            {
                return _Color;
            }
        }
            ENDCG
        }
    }
}