Create color changer in strumpy shader editor

I am curious on how to make a shader that changes my font color from black to white and vice versa. I have played around with this a bit, and am unsure how to do this.
I basically want to emulate this:

Example of text that changes color based on progress bar before it

I am curious how to do this. I wanted to compare the rgba values to all zero, or to all black, but i am unsure how to do this. I would guess you would use step, or any or the all nodes, but am unsure. How would i split the rgba values to their respective components? Similar to Vector2 split node.

I tried using the Assemble node and fed in 4 float values, and then wired the result to diffuse, but to no avail. It only stays white (assuming from wrong input type and defaulting to all zero).

And will strumpy shaders work for guiTexture fonts and for when they are overlapped and blocked, to be rendered still?

How would i accomplish this? I am unsure how to start on this…

following script will help you to blend your font texture or material

Shader “Myshaders/ChangeMaterial” {

Properties {

    _Tint ("Main Color", Color) = (.9, .9, .9, 1.0)

    _TexMat1 ("Base (RGB)", 2D) = "white" {}

    _TexMat2 ("Base (RGB)", 2D) = "white" {}
	_TexMat3 ("Base (RGB)", 2D) = "white" {}

    _Blend ("Blend", Range(0.0,1.0)) = 0.0


Category {

    ZWrite On

    Alphatest Greater 0

    Tags {Queue=Transparent}

    Blend SrcAlpha OneMinusSrcAlpha

    ColorMask RGB

SubShader {

    Pass {


        Material {

            Diffuse [_Tint]

            Ambient [_Tint]


        Lighting On

        SetTexture [_TexMat1] { combine texture }

        SetTexture [_TexMat2] { constantColor (0,0,0,[_Blend]) combine texture lerp(constant) previous }

        SetTexture [_TexMat2] { combine previous +- primary, previous * primary }



FallBack " Diffuse", 1