If that’s the case, you are already converting to html format. The question becomes where are you presenting it?
If you write something in HTML format, it will present itself as html if that medium supports HTML.
To state the obvious, If you output your text in html format in a text file and save it as a .html file, it will display your text as HTML when opened in a Browser but not when you open it in Notepad.
Not to forget, a properly formed html is recommended to be:
<html>
<head>meaningful title </head>
<body>
<ol>
1. Your line here=>Green
2. Your line here=>Red
3. Your line here=>Red
</ol>
</body>
</html>