You could write a JS script and use Tempermonkey or Greasemonkey depending on your browser, I'm not sure what you tried to do which lead you to w3school website referring to 404 page not found.
The color code developer use is HEX:#66CD00;
PS;
This does not belong to suggestion section, as there are no dead links to the forum which ever lead or referred to an undefined page, moved to help & support.
