Those markings are the the aircraft's identifying markings to denote its group, squadron, and the aircraft's position within the squadron. Essentially this allowed for quick identification of a friendly aircraft and corroboration of its radio callsign.

The second plane (44-R), for example, can be identified as part of 381st Bombardment Group by the "L" in a triangle on its red empennage, itself part of 1st Bomb Wing/1st Air Division of the 8th Air Force and the 381st BG crest on its nose. There might be a little bit of creative license at play here since I can't find any record of a liaison squadron flying the L-4 attached to 381st BG, but I might have misidentified things.

The "44-R" would in turn designate the specific wing or squadron within that group, and the 'R' is the specific aircraft within that squadron.