Workflowy currently does not allow you to change the font size but we do allow you to choose from a set of font styles.
Please note, the font settings are "global" and affect the fonts anywhere you type. You cannot however select one block of text and change the font.
We allow you to select any block of text and make it bold, italic or underlined. Simply highlight the text, and use the following keyboard commands:
For bold, use the CTRL + B keys
For italic, use the CTRL + I keys
For underline, use the CTRL + U keys
We do not allow color formatting currently, but you may reference this article for some 3rd party solutions:
You can also change the "Theme", which will provide a variation of the look and feel of the font and background colors.
With the Pro membership, you can access more fonts and themes....but please note, the additional themes will only be visible if you are using the web version of Workflowy, but not on Chrome Desktop or mobile.