Sprite/Vertex Colored, Fast Black and White Shader

I'm looking to use the Sprite/Vertex Colored, Fast shader. I'm not familiar with customizing shaders, and was wondering if someone could help make the Sprite/Vertex Colored, Fast shader black and white.

Here is the shader. I feel like I should be able to add a simple line of code to make it black and white.

Shader "Sprite/Vertex Colored, Fast" { Properties { _MainTex ("Particle Texture", 2D) = "white" {} }

Category { Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" } Blend SrcAlpha OneMinusSrcAlpha Cull Off Lighting Off ZWrite Off Fog { Color (0,0,0,0) } BindChannels { Bind "Color", color Bind "Vertex", vertex Bind "TexCoord", texcoord } SubShader { Pass { SetTexture [_MainTex] { combine texture * primary } } } } }

Thanks!