[JeremyJaydan]

You can right click the 'pasteboard' and change it to gray.

[garganzol]

Thanks for the tip. There are some predefined colors out there, but all of them either too dark (darker shades of gray) or too bright (white). My spatial brain needs #e5e5e5 to function properly, but it seems impossible to set that in Affinity 3.0.

Edit: never mind, found it at Settings -> User Interface -> Artboard Background Gray Level.