From Wikipedia

In February 1944, the 2nd Division authorized the use of war-weary aircraft specially fitted to aid assembly of individual group formations. Known as Assembly or Formation Ships, they were equipped with signal lighting, provision for quantity discharge of pyrotechnics, and featured distinctive individual paint schemes of psychedelic colors in stripes, checkers, or polka dots to enable easy recognition by their flock of bombers. The aircraft used in the first allocation were B-24Ds retired by the 44th, 93rd and 389th Groups. Arrangements for signal lighting varied from group to group, but generally consisted of white flashing lamps on both sides of the fuselage arranged to form the identification letter of the group. All armament and armor was removed, and in some cases the tail turret. In the B-24Hs used for this purpose, the nose turret was removed and replaced by a "carpetbagger" type nose. Following incidents when flare guns were accidentally discharged inside the rear fuselage, some Formation Ships had pyrotechnic guns fixed through the fuselage sides. As these aircraft normally returned to base once a formation had been established, a skeleton crew of two pilots, navigator, radio operator and one or two flare discharge men were carried. In some groups an observer officer flew in the tail position to monitor the formation. These aircraft became known as Judas Goats.