This recommendation came in from @jasonh at office hours. He was looking to increase the font size of graph titles, legends, and labels on the dashboards page. Currently, it does not appear that there’s any ability to manipulate the styling or text of these aspects inside the analytics editor, or from the dashboard page.
I have good news for regarding this topic. The functionality to change font sizes for text in charts within Apps will be part of the next release (Release 249).
The release comes with even more new formatting-related features for analytics like a new formatting panel, custom axis titles and more. You can check out the release notes with GIFs showing the features here.