Press Settings in the top view.
Then select a theme, e.g. Minimalistic or Chrome Rings.
As a supplement to these appearances, it is possible to choose between Normal and Bright. With Normal, the screen background is dark and the text is light. This alternative is the default for all themes. A light variant can also be selected, in which the background is light and the text is dark. This alternative can be useful in e.g. strong daylight.
This alternative is always available for the user and is not affected by the surrounding lighting.