When making the switch to MA-1 jackets, which occurred between 1949 to 1950, a few changes were made to the B-15 style. Most notably, the fur collar was replaced with a knit collar, primarily because the fur collar got in the way of the parachute harness. An orange liner was added to help promote rescue visibility in the event of a plane crash, making the jacket reversible. A nylon body became the standard due to the relatively new (at the time) material's ability to remain dry and prevent rain or water from soaking into the jacket.
While we associate the Army's “sage green” with just about anything military related, the original color of bomber jackets were in a “midnight blue.” During the course of the Korean War, and especially during the beginning of the '60s and the Vietnam War era, the jacket was shifted to the sage green color in order to more effectively camouflage soldiers in countrysides with dense vegetation and plant life.