Hi! To find the available options to change the background of the app, find by opening the Smartthings app - click on the house at the top left - Manage locations - [Click on your home] - Location wallpaper
Should you find that the available options do not match the color you want, it is fine to download a black image from e.g. Google and then select that image from the Gallery option under the Location wallpaper category.
We hope you find an alternative that enhances your experience of the app!