Hi Fernando, sorry for the lack of clarity. This is happening with container blocks on three separate sites I have checked so far, which all have GeneratePress pro, and GenerateBlocks pro installed.
When I attempt to set a background color in the block settings, the preview of the container immediately disappears and it says: ‘This block has encountered an error and cannot be previewed.’
I had added background colors to container blocks before without difficulty, so this is not an issue with adding the color incorrectly.
Adding a background color to an ordinary WordPress paragraph block still works fine.
The site has the most recent version of WordPress (I think this updated a few days ago – all plugins etc are up to date).
Any ideas most appreciated!