Hi Adele,
Today, only the text size is possible for now. To do so, you can double click on your text and use the H1 H2 H3 options.

If you wish to have more text formatting options, the best way is to create an idea on the Community so other users can upvote. It will then be taken into account on our roadmap according to its priority.
Many thanks.
Benoit
Hi @Adelgo! Since your original post we have added the possibility to change the background color and text color in text widgets. Check out this article for more information:
Thanks, Sharon