Transparent Vertex Shader blend with color?

Questions & Answers
1

How could I make this shader to blend with the color i declared in the properties?

Shader "AShader" {
Properties {
	_Color ("Main Color", Color) = (1,1,1,1)
	_MainTex ("Base (RGB) Alpha (A)", 2D) = "white" {}
	_Cutoff ("Alpha cutoff", Range(0,1)) = 0.5
}

SubShader {
	Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" "LightMode"="ForwardBase"}
	LOD 100
	Cull Off
	ZWrite Off
	Blend SrcAlpha OneMinusSrcAlpha 
	
	
	CGINCLUDE
	#include "UnityCG.cginc"
	sampler2D _MainTex;
	half4 _MainTex_ST;
	
	float4 _GrassWind; //is not defined in terrainengine.cginc

	struct v2f {
		float4 pos : SV_POSITION;
		float2 uv : TEXCOORD0;
	};

inline float4 AnimateGrass(float4 pos, float3 normal, float animParams)
{	
	pos.xyz += animParams * _GrassWind.xyz * _GrassWind.w; // controlled by vertex color blue
	return pos;
}
	
	v2f vert (appdata_full v)
	{
		v2f o;
		float4	windParams	= float(v.color.b);		

		float4 mdlPos = AnimateGrass(v.vertex, v.normal, windParams);
		o.pos = mul(UNITY_MATRIX_MVP,mdlPos);
		o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
		return o;
	}
	ENDCG

	Pass {
		CGPROGRAM
		#pragma debug
		#pragma vertex vert
		#pragma fragment frag
		#pragma fragmentoption ARB_precision_hint_fastest		
		fixed4 frag (v2f i) : COLOR
		{
			fixed4 tex = tex2D (_MainTex, i.uv);
			
			fixed4 c;
			c.rgb = tex.rgb;
			c.a = tex.a;
			
			return c;
		}
		ENDCG 
	}	
}
}
2

Like this?

Shader "AShader" {
Properties {
    _Color ("Main Color", Color) = (1,1,1,1)
    _MainTex ("Base (RGB) Alpha (A)", 2D) = "white" {}
    _Cutoff ("Alpha cutoff", Range(0,1)) = 0.5
}
 
SubShader {
    Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" "LightMode"="ForwardBase"}
    LOD 100
    Cull Off
    ZWrite Off
    Blend SrcAlpha OneMinusSrcAlpha 
 
 
    CGINCLUDE
    #include "UnityCG.cginc"
    sampler2D _MainTex;
    half4 _MainTex_ST;
    half4 _Color;
 
    float4 _GrassWind; //is not defined in terrainengine.cginc
 
    struct v2f {
       float4 pos : SV_POSITION;
       float2 uv : TEXCOORD0;
    };
 
inline float4 AnimateGrass(float4 pos, float3 normal, float animParams)
{   
    pos.xyz += animParams * _GrassWind.xyz * _GrassWind.w; // controlled by vertex color blue
    return pos;
}
 
    v2f vert (appdata_full v)
    {
       v2f o;
       float4    windParams = float(v.color.b);     
 
       float4 mdlPos = AnimateGrass(v.vertex, v.normal, windParams);
       o.pos = mul(UNITY_MATRIX_MVP,mdlPos);
       o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
       return o;
    }
    ENDCG
 
    Pass {
       CGPROGRAM
       #pragma debug
       #pragma vertex vert
       #pragma fragment frag
       #pragma fragmentoption ARB_precision_hint_fastest     
       fixed4 frag (v2f i) : COLOR
       {
         fixed4 tex = tex2D (_MainTex, i.uv);
 
         fixed4 c;
         c.rgb = tex.rgb;
         c.a = tex.a;
 
         return c * _Color;
       }
       ENDCG 
    }  
}
}

You have to declare the color like this:

    sampler2D _MainTex;
    half4 _MainTex_ST;
    half4 _Color; // see the color added to these lines.

Then you can just multiply the output color with the color you want it blended with:

return c * _Color;