Unity2D: Remove Shader Colour

Hi, I have a shader that I found to help me with a battle transition, I've done all my scripting for it; and it does work, I only have one problem with the shader I found, which is the colour. I want to remove the colour within the shader or at least make it transparent so that the natural texture colour can show! I tried removing anything to do with colour in the shader script, but I got an error and it also made my shader pink! It would me much appreciated if anyone can help me! Thank you :)

The error:

Shader error in 'Hidden/BattleTransitions': 'lerp': no matching 2 parameter intrinsic function; Possible intrinsic functions are: lerp(float|half|min10float|min16float, float|half|min10float|min16float, float|half|min10float|min16float) at line 104 (on d3d11) Compiling Vertex program Platform defines: UNITY_ENABLE_REFLECTION_BUFFERS UNITY_PBS_USE_BRDF1 UNITY_SPECCUBE_BOX_PROJECTION UNITY_SPECCUBE_BLENDING

The Script:

    Shader "Hidden/BattleTransitions"
    {
      Properties
      {
       _MainTex("Texture", 2D) = "white" {}
     _  TransitionTex("Transition Texture", 2D) = "white" {}
     _Color("Screen Color", Color) = (1,1,1,1)
     _Cutoff("Cutoff", Range(0, 1)) = 0
     [MaterialToggle] _Distort("Distort", Float) = 0
     _Fade("Fade", Range(0, 1)) = 0
 }

     SubShader
     {
         // No culling or depth
         Cull Off ZWrite Off ZTest Always

         Pass
         {
             CGPROGRAM
             #pragma vertex vert
             #pragma fragment frag

             #include "UnityCG.cginc"

             struct appdata
             {
                 float4 vertex : POSITION;
                 float2 uv : TEXCOORD0;
             };

             struct v2f
             {
                 float2 uv : TEXCOORD0;
                 float2 uv1 : TEXCOORD1;
                 float4 vertex : SV_POSITION;
             };

             float4 _MainTex_TexelSize;

             v2f simplevert(appdata v)
             {
                 v2f o;
                 o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
                 o.uv = v.uv;
                 return o;
             }

             v2f vert(appdata v)
             {
                 v2f o;
                 o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
                 o.uv = v.uv;
                 o.uv1 = v.uv;

                 #if UNITY_UV_STARTS_AT_TOP
                 if (_MainTex_TexelSize.y < 0)
                     o.uv1.y = 1 - o.uv1.y;
                 #endif

                 return o;
             }

             sampler2D _TransitionTex;
             int _Distort;
             float _Fade;

             sampler2D _MainTex;
             float _Cutoff;
             fixed4 _Color;

             fixed4 simplefrag(v2f i) : SV_Target
             {
                 if (i.uv.x < _Cutoff)
                     return _Color;

                 return tex2D(_MainTex, i.uv);
             }

             fixed4 simplefragopen(v2f i) : SV_Target
             {
                 if (0.5 - abs(i.uv.y - 0.5) < abs(_Cutoff) * 0.5)
                     return _Color;

                 return tex2D(_MainTex, i.uv);
             }

             fixed4 simpleTexture(v2f i) : SV_Target
             {
                 fixed4 transit = tex2D(_TransitionTex, i.uv);

                 if (transit.b < _Cutoff)
                     return _Color;

                 return tex2D(_MainTex, i.uv);
             }

             fixed4 frag(v2f i) : SV_Target
             {
                 fixed4 transit = tex2D(_TransitionTex, i.uv1);

                 fixed2 direction = float2(0,0);
                 if(_Distort)
                     direction = normalize(float2((transit.r - 0.5) * 2, (transit.g - 0.5) * 2));

                 fixed4 col = tex2D(_MainTex, i.uv + _Cutoff * direction);

                 if (transit.b < _Cutoff)
                     return col = lerp(col, _Color, _Fade);

                 return col;
             }                    
             ENDCG
         }
     }

}