How to change Physarum background color?

[Vamoss]

Hello again Amanda,

I am trying to change the default black background color without success.

We can also refer to this example in the further code:
https://openprocessing.org/sketch/1760726

I tried to change the render fragment shader from this:

in vec2 v_uv;
uniform sampler2D u_trail;
uniform float u_scale;
out vec4 out_state;
void main() {
	out_state = vec4(texture(u_trail, v_uv).xyz * u_scale, 1);
}

To this:

in vec2 v_uv;
uniform sampler2D u_trail;
uniform float u_scale;
out vec4 out_state;
float luma(vec3 color) {
	return dot(color, vec3(0.299, 0.587, 0.114));
}
void main() {
	vec3 trailColor = texture(u_trail, v_uv).xyz * u_scale;
	float brightness = luma(trailColor );
	vec3 backgroundColor = vec3(1.0, 0.0, 0.0);
	vec3 mixedColor = mix(backgroundColor, trailColor , brightness);
	out_state = vec4(vec3(mixedColor), 1);
}

The result is almost there, but the mixedColor borders are not smooth.

Thank you once again,
Carlos