Well you could, but you can have a Boxes tab Condition that tests for 1841 Census Event and 1851 Census Event and 1861 Census Event that sets Box Colour green.

That way you don’t have to keep setting Flags to show you have the associated Census Event, because the Condition looks directly at the facts.

See the FHUG Knowledge Base FH Using Flags and Icons and Expressions:

https://www.fhug.org.uk/wiki/doku.php?id=how_to:using_flags_and_icons_and_expressions

Regards, Mike Tate