Hi John, thanks for your input.
What I'm thinking about is this simple idea: #+TAGGROUP: :colour: :red:green: in such a way that: 1. searches for :red: will continue to display entries with :red: 2. searches for :colour: will display entries with :red: and/or :green: Would this be useful already? Would this go into the right direction for solving your problem? Thanks, -- Bastien