Themes
There is a settings gear icon that can be accessed at the top right navigation in the toolbar within the application. It brings up a dialog to change themes by name (basically, effectively allowing users to select their choice of customizable color palettes -- "cyberpunk" hacker app style, quoth someone years ago):
Historically, in the days pre my Fall 2020 discourse with Google about its choice of ethics and bad behavior, the distinction between the Free and Paid flavors of the application on Play Store (for Android devices) was an extra set of user themes. Those options disabled in the above image may eventually be incorporated into all releases of the application off of Play Store. Anyone who choses to roll their own binary for my application, can of course automatically chose to install the Paid flavor by default with Droid platform developer options (now the recommended install route).