Shader Pallet Swap Godot 4 (ColorRect)

Shader Pallet Swap  Godot 4 (ColorRect)

shader_type canvas_item;

uniform vec4 whiteColor : source_color = vec4(0.961, 0.980, 0.937, 1.0);
uniform vec4 lightGreyColor : source_color = vec4(0.549, 0.749, 0.039, 1.0);
uniform vec4 darkGreyColor : source_color = vec4(0.18, 0.451, 0.125, 1.0);
uniform vec4 blackColor : source_color = vec4(0.0, 0.247, 0.0, 1.0);
uniform sampler2D SCREEN_TEXTURE : hint_screen_texture, filter_linear_mipmap;

float min4(float a, float b, float c, float d){
    return min(a, min(b, min(c, d)));
}

void fragment(){
    vec4 currentColor = texture(SCREEN_TEXTURE, SCREEN_UV);

    float blackDistance = distance(currentColor, vec4(vec3(0.0), 1.0));
    float whiteDistance = distance(currentColor, vec4(vec3(1.0), 1.0));
    float lightGrayDistance = distance(currentColor, vec4(vec3(0.666, 0.666, 0.666), 1.0));
    float darkGrayDistance = distance(currentColor, vec4(vec3(0.333, 0.333, 0.333), 1.0));

    if (
        whiteDistance == min4(whiteDistance, lightGrayDistance, darkGrayDistance, blackDistance)
    )
    {
        COLOR = whiteColor;
    }
    else if (
        blackDistance == min4(whiteDistance, lightGrayDistance, darkGrayDistance, blackDistance)
    )
    {
        COLOR = blackColor;
    }
    else if (
        darkGrayDistance == min4(whiteDistance, lightGrayDistance, darkGrayDistance, blackDistance)
    )
    {
        COLOR = darkGreyColor;
    }
    else if (
        lightGrayDistance == min4(whiteDistance, lightGrayDistance, darkGrayDistance, blackDistance)
    )
    {
        COLOR = lightGreyColor;
    }
    else{
        COLOR = whiteColor;
    }
}