If you create a game offline and click on "build", you will notice it creates, among others, a style.css file. There you can change the link colour and add other colours as well (for example for p (paragraph)). As far as I can tell from the Wiki, there's no way to change CSS in the web editor, except using this (not recommended) approach for adding styles to a HTML element directly:
<p style="color: Red;">This is a red paragraph</p>
Thank you good sir! It worked! Mind if you teach me how to add an image to the background as well? I haven't been able to make that work.