You can use Vim! It’s probably installed already if you’re on modern Linux/MacOS and an easy install if not.
:syntax will turn syntax highlighting on and :hardcopy will print it. There’s syntax highlighting definitions for many languages out there. The default look is usually optimised for screen display, but you can fix that.
Simply open the file on command line with vim <filename>, type :syntax on<ENTER>, then :hardcopy<ENTER> to print it. Quit Vim with :q!<ENTER>.
There’s also the :TOhtml command which will open the current selection as HTML in a new Vim window. Capture the entire document with :%y<ENTER> followed by :TOhtml<ENTER> to open it.