Blankstrap 5 comes with the default Bootstrap styling.
Themes are based on a bootstrap CSS file. This can be set inside the Blankstrap Core stack.
In order to apply predefined Bootstrap themes, you could for example download them from Bootswatch.com.
Add this file to the RW resources and link it inside the Blankstrap 5 core stack. The updated styling will be visible in preview mode and when published.
Building your own theme is easy using services like Themestr.app or Bootstrap Build. These allow you to build you own theme in various steps. Download the generated Bootstrap CSS file and reference it like shown above.
Switching to a dark mode theme is by default turned of. You are able to turn it on inside the Blankstrap Core stack. You are able to select a standard supplied dark theme or a custom theme.
If the device is set to dark mode is evaluated by the standard CSS media query @media (prefers-color-scheme: dark). Read more about this media query here. Chaning the device to dark mode will then automatically switch to the selected dark mode theme.
In oder to style the different components coming with Blankstrap, knowledge about Boostrap styling and usage of Bootstrap styling classes is required. Each component contains a CSS input field in oder to apply CSS classes, for example margin or padding styling. The following example applies a vertical margin 3 on a button (my-3). More information about Bootstrap styling classes can be found in the official documentation of Bootstrap 5.
Still youre able to use other stacks and theri inbuild functionality for styling. Using the Blankstrap stacks is not required.