Depending on the use case you have for the Time Series Data Service, it makes sense that you use, for example, a dark mode or a light mode. You can easily set this, the setting for this is saved in your profile, so that this setting still applies the next time you log in.
To change the display mode, simply click on the avatar at the bottom of the left navigation bar – this will open some settings. Scroll down to the “Preferences” section and choose your UI theme. Click on [Save] in the corresponding area to save the settings.