HLSL TextureSampler Color returning white

Question

I was following a tutorial to build a basic effect texture in XNA/Monogame. Everything seems to be working but if Percentage = 0 it will always return the color as white. I am having a hard time wrapping my head around why this would be happening. Here is the relevant hlsl code

float Percentage;

sampler TextureSampler: register(s0);
float4 PixelShaderFunction(float4 pos : SV_POSITION, float4 color1 : COLOR0, float2 Tex : TEXCOORD0) : SV_TARGET0
{
    float4 Color = tex2D(TextureSampler, Tex).abgr;
    float a = Color.a;
    float r = Color.r;
    float g = Color.g;
    float b = Color.b;
    Color.rgb = dot(Color.rgb, float3(0.7 * Percentage, 0.59 * Percentage, 0.11 * Percentage));
    r = r - (r - Color.rgb) * Percentage;
    g = g - (g - Color.rgb) * Percentage;
    b = b - (b - Color.rgb) * Percentage;
    Color.a = a;
    Color.r = r;
    Color.g = g;
    Color.b = b;
    return Color;
}


technique hit
{
    pass Pass1
    {
        PixelShader = compile ps_3_0 PixelShaderFunction();
    }
}

When I set the argb to color1.argb then it outputs the proper color but it renders as a solid square rather than what the actual object is (a circle in this case)

Answer 1

I have fixed this by changing

float4 Color = tex2D(TextureSampler, Tex).abgr; 

to

float4 Color = tex2D(TextureSampler, Tex).abgr * color1;