let red = 51; 
let green = 255;
let blue = 51;
let alpha = 128;

let mut html_color = 
format!("#{:X}{:X}{:X}", 
    red, green, blue);
println!("style=\"color: {html_color}\"");

//with transparency
html_color = format!("{html_color}{:X}", 
    alpha);
println!("html_color is {html_color}");