Brave allows you to display the app in light or dark mode to suit your preference. To change the browser theme on Android:

1. Launch Brave and tap Main menu --> Settings.
2. Scroll down to the Display section and tap Appearance.
3. Tap the Theme option displayed at the top of the Appearance page:
   

Here you will find the main theme options available.

• System Default: Selecting this option makes the browser match whatever the theme setting is set for on your device's OS settings. 
• Light: Changes the browser to use "light" theme.
• Dark: Changes the browser to use "dark" theme.

Light theme enabled

Dark theme enabled

Experimental "Night" Mode

In addition to the options above, the Appearance page also has the option to toggle on the experimental "Night Mode" option. When this option is enabled, the browser theme will be "dark" automatically and in addition, the browser will attempt to force the content of a webpage being viewed to display in a "dark theme". 

Night mode enabled

It is worth noting that this particular setting may result in some web pages displaying incorrectly. This is typically because this feature works by the browser detecting colors displayed on the webpage being viewed as "light" and attempting to change or invert them to display "dark" colors instead. However, depending on the color values used on the site, an inverted value of a particular color may not actually be ideal for viewing that content. For example, a site with a white background and gray text may get inverted to display a black background with dark-gray text, resulting in the content being difficult to read.