Question about metaballs to create a influence map

I have this shader code, and i want use more than 4 colours, how can i do it. Now, the shader picks 4 main channels and creates an insolate edge usign it, how can i extend it to use more than 4 colours

Shader "Hidden/Metaballs" { Properties { _MainTex("Texture", 2D) = "white" {} }

 SubShader
 {
     Cull Off ZWrite Off ZTest Always
 
     //Draw metaball
     Pass
     {
         CGPROGRAM
         #pragma vertex vert
         #pragma fragment frag
         #include "UnityCG.cginc"
         struct appdata { float4 p : POSITION; float2 uv : TEXCOORD0; };
         struct v2f { float2 uv : TEXCOORD0; float4 p : SV_POSITION; };
         v2f vert(appdata v) { v2f o; o.p = UnityObjectToClipPos(v.p); o.uv = v.uv; return o; }
 
 
         struct Emitter
         {
             float3 position;
             float radius;
             float4 channels;
         };
 
         sampler2D _MainTex;
         float _Metaball_Smooth;
         int _EmitterCount;
         StructuredBuffer<Emitter> _Emitters;
 
         //smin from Inigo Quilez adapted for a float4
         float4 smin(float4 a, float4 b, float k)
         {
             float4 res = exp2(-k * a) + exp2(-k * b);
             return -log2(res) / k;
         }
 
         float4 frag(v2f i) : SV_Target
         {
             float4 col = 0.0;
             float2 pos = i.uv * 2.0 - 1.0;
             for (int j = 0; j < _EmitterCount; j++)
             {
                 Emitter emitter = _Emitters[j];
 
                 float dist = distance(pos, emitter.position.xz);
                 float factor = dist - emitter.radius;
                 col = lerp(col, smin(col, factor, _Metaball_Smooth), emitter.channels);
             }
             return col;
         }
         ENDCG
     }
 
 
     //Select main color
     Pass
     {
         CGPROGRAM
         #pragma vertex vert
         #pragma fragment frag
         #include "UnityCG.cginc"
         struct appdata { float4 p : POSITION; float2 uv : TEXCOORD0; };
         struct v2f { float2 uv : TEXCOORD0; float4 p : SV_POSITION; };
         v2f vert(appdata v) { v2f o; o.p = UnityObjectToClipPos(v.p); o.uv = v.uv; return o; }
 
 
         sampler2D _MainTex;
         float _Metaball_Smooth;
 
         float4 frag(v2f i) : SV_Target
         {
             float4 col = tex2D(_MainTex, i.uv);
             float minValue = min(min(col.r, col.g), min(col.b, col.a)) + 0.01;
             float alpha = step(minValue, -(1.0 / _Metaball_Smooth));
             if (col.r < minValue)
                 return float4(0.9, 0, 0, 0) * alpha;
             else if (col.g < minValue)
                 return float4(0, 0.9, 0, 0) * alpha;
             else if (col.b < minValue)
                 return float4(0, 0, 0.9, 0) * alpha;
             else if (col.a < minValue)
                 return float4(0, 0, 0, 0.9) * alpha;
             return float4(0, 0, 0, 0);
         }
         ENDCG
     }
 
     //Blur
     Pass
     {
         CGPROGRAM
         #pragma vertex vert
         #pragma fragment frag
         #include "UnityCG.cginc"
         struct appdata { float4 p : POSITION; float2 uv : TEXCOORD0; };
         struct v2f { float2 uv : TEXCOORD0; float4 p : SV_POSITION; };
         v2f vert(appdata v) { v2f o; o.p = UnityObjectToClipPos(v.p); o.uv = v.uv; return o; }
 
 
         sampler2D _MainTex;
         float4 _MainTex_TexelSize;
         int _BlurItterations;
         float2 _BlurRange;
 
         float4 frag(v2f i) : SV_Target
         {
             float4 col = float4(0.0, 0.0, 0.0, 0.0);
             float sum = 0.0;
 
             for (int j = 0; j < _BlurItterations; j++)
             {
                 float t = ((float)(_BlurItterations - j) / _BlurItterations);
                 col += tex2D(_MainTex, i.uv + _BlurRange * j * _MainTex_TexelSize.xy) * t;
                 col += tex2D(_MainTex, i.uv - _BlurRange * j * _MainTex_TexelSize.xy) * t;
                 sum += t * 2;
             }
             return col / sum;
         }
         ENDCG
     }
 
        
     //Isolate Edges
     Pass
     {
         CGPROGRAM
         #pragma vertex vert
         #pragma fragment frag
 
         #include "UnityCG.cginc"
 
         struct appdata
         {
             float4 vertex : POSITION;
             float2 uv : TEXCOORD0;
         };
 
         struct v2f
         {
             float2 uv : TEXCOORD0;
             float4 vertex : SV_POSITION;
         };
 
         v2f vert(appdata v)
         {
             v2f o;
             o.vertex = UnityObjectToClipPos(v.vertex);
             o.uv = v.uv;
             return o;
         }
 
         sampler2D _MainTex;
         float _EdgeThickness;
 
         float4 _RedChannelColor;
         float4 _GreenChannelColor;
         float4 _BlueChannelColor;
         float4 _AlphaChannelColor;
 
         float4 frag(v2f i) : SV_Target
         {
             float4 col = tex2D(_MainTex, i.uv);
             float4 gradient = (1.0 - col) * smoothstep(0.5, 0.55, col);
             float4 edge = smoothstep(0.4 - _EdgeThickness, 0.45 - _EdgeThickness, gradient);
 
             float4 result = gradient + edge;
 
             return _RedChannelColor * result.r +
                 _GreenChannelColor * result.g +
                 _BlueChannelColor * result.b +
                 _AlphaChannelColor * result.a;
         }
         ENDCG
     }
 }

}

i want add more colors to regions