I would put a red ribbon on the tail for everything. Halter and riding both. (at all the shows I've been to) in halter when you line up people usually put a horse length between you and them anyway but when the judge comes around for inspection they pass between two horses just within kicking range it seems. So for halter if there is a ribbon in the tail it would let the judge know keep their distance too
He knows when you're happy, He knows when you're comfortable, He knows when you're confident, And he always knows when you have carrots.