Updating the Hivemanager will not cause any lapse in service on your wireless network. The lights on the APs will change color, only because at some point they will lose their CAPWAP connection to the HM, but will still operate fine. When/If you update the firmware on the APs there will be an interruption in service as the APs will need to reboot to apply the new firmware.
Back up the database and store it in a safe place before updating HiveManager software. For Help in backing up your database, see "Back up the Database". (In the HiveManager Help file)