Adding tint color variable to shader

hey

I'm a bit confused on shaders and programming them. I've looked at some other questions like this on unity Q&A but I still didn't totally understand what to do.

I'm trying to add a tint colour variable to the shader Particles/Additive (soft) but don't know how to do this. I have the source code here:

 Shader "Particles/Additive (Soft)" {
 Properties {
     _MainTex ("Particle Texture", 2D) = "white" {}
     _InvFade ("Soft Particles Factor", Range(0.01,3.0)) = 1.0
 }
 
 Category {
     Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" }
     Blend One OneMinusSrcColor
     ColorMask RGB
     Cull Off Lighting Off ZWrite Off Fog { Color (0,0,0,0) }
     BindChannels {
         Bind "Color", color
         Bind "Vertex", vertex
         Bind "TexCoord", texcoord
     }
 
     // ---- Fragment program cards
     SubShader {
         Pass {
         
             CGPROGRAM
             #pragma vertex vert
             #pragma fragment frag
             #pragma fragmentoption ARB_precision_hint_fastest
             #pragma multi_compile_particles
 
             #include "UnityCG.cginc"
 
             sampler2D _MainTex;
             fixed4 _TintColor;
             
             struct appdata_t {
                 float4 vertex : POSITION;
                 fixed4 color : COLOR;
                 float2 texcoord : TEXCOORD0;
             };
 
             struct v2f {
                 float4 vertex : POSITION;
                 fixed4 color : COLOR;
                 float2 texcoord : TEXCOORD0;
                 #ifdef SOFTPARTICLES_ON
                 float4 projPos : TEXCOORD1;
                 #endif
             };
 
             float4 _MainTex_ST;
             
             v2f vert (appdata_t v)
             {
                 v2f o;
                 o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
                 #ifdef SOFTPARTICLES_ON
                 o.projPos = ComputeScreenPos (o.vertex);
                 COMPUTE_EYEDEPTH(o.projPos.z);
                 #endif
                 o.color = v.color;
                 o.texcoord = TRANSFORM_TEX(v.texcoord,_MainTex);
                 return o;
             }
 
             sampler2D _CameraDepthTexture;
             float _InvFade;
             
             fixed4 frag (v2f i) : COLOR
             {
                 #ifdef SOFTPARTICLES_ON
                 float sceneZ = LinearEyeDepth (UNITY_SAMPLE_DEPTH(tex2Dproj(_CameraDepthTexture, UNITY_PROJ_COORD(i.projPos))));
                 float partZ = i.projPos.z;
                 float fade = saturate (_InvFade * (sceneZ-partZ));
                 i.color.a *= fade;
                 #endif
                 
                 half4 prev = i.color * tex2D(_MainTex, i.texcoord);
                 prev.rgb *= prev.a;
                 return prev;
             }
             ENDCG 
         }
     }     
 
     // ---- Dual texture cards
     SubShader {
         Pass {
             SetTexture [_MainTex] {
                 combine texture * primary
             }
             SetTexture [_MainTex] {
                 combine previous * previous alpha, previous
             }
         }
     }
     
     // ---- Single texture cards (does not do particle colors)
     SubShader {
         Pass {
             SetTexture [_MainTex] {
                 combine texture * texture alpha, texture
             }
         }
     }
 }
 }

So I'm trying to add a tint colour variable to that. I'm not sure if its a large or small job to add it to this shader. Thanks for all replies in advance.

EDIT:

Thanks for your reply cgcookie, your upcoming shader vids look good too, unfortunately the code your gave me produced these errors: see pic