Yes, it is possible to change the background colour of the Apple Watch SE 2024. You can customise the dial using the Apple Watch app on your iPhone or directly on the watch.

- You can choose a new dial and adjust the colours, symbols, and style of the dial via the Apple Watch app on your iPhone.
- You can also use third-party applications such as Dials or Clockology to access a variety of wallpapers and customise the dial to suit your preferences.

In addition, you can use the 'Photo' dial to choose one of your personal photos as a wallpaper and adjust the associated colour and style settings.