Help with HTML code to get HTML page in Lovelace iFrame to obey themes

I am neophyte to HTML, CSS and javascript, wonder if someone could point me to a simple example that I could incorporate.

I have a python program that generates a static HTML page with some tabular data within HA’s www directory structure. Have it rendering and refreshing within a Lovelace iFrame card fine.

What I would like to add to the HTML that I am creating is the proper HTML, CSS or javascript to instruct the page to use the current theme’s foreground and background colors.

Hope this makes sense, thanks in advance!

outline of what I a currently generating :

    <!DOCTYPE html>
    <html lang="en">
        <meta charset="utf-8">
        setTimeout(function() {
            }, 30000)



        <br />