This applies to the current generation of Launchpad
With the Launchpad (not original Launchpad or Launchpad S), it is possible to change the MIDI Channel for User 1 and User 2 mode. It’s important to bear this in mind if you’re trying to set up a lightshow by sending MIDI data to the Launchpads user modes. Make sure you're always sending data to/receiving data from the correct MIDI channel as set up here.
To set the MIDI channels for User 1 and User 2 mode, enter boot loader mode by powering the unit on while holding the ‘Session’, ‘User 1’, ‘User 2’ and ‘Mixer’ buttons. The top two rows of orange pads are used to set the device ID (1-16). The third row of pads is used to set the User 1 MIDI channel. The first 5 are red and not available, User 1 mode can be set to MIDI channel 6, 7 or 8 by pressing the blue pads. Similarly, the fourth row of pads is used to set the User 2 MIDI channel, the first 5 are red and not available, User 2 mode can be set to MIDI channel 14, 15 or 16 by pressing the blue pads.
Further information can be found in the advanced features guide here.