Breaking the Mold
With the coming of Wrath of Khan, the Monster Maroon became the officer's choice in uniforms. But even in that film, some variations emerged, most notably a maroon vest theat Admiral Kirk wore beneath his Field Jacket in place of the standard maroon jacket. This design would be used again in Star Trek III, this time by Saavik. Throughout most of that film, Saavik wears a brown leather vest beneath her Field Jacket. In Star Trek IV, Scotty gets his own version of a vest, this time for everyday use on board the Enterprise. His had various pockets, ostensibly intended to accomodate his many engineering tools and gadgets.
Star Trek III would also introduce a new jacket – the so-called "bomber" style, named after the jacker worn by WWII Bomber pilots. Starfleet Commander Morrow and Scotty both sport their own versions of the bomber while Kirk would get one in Star Trek V. By the time Star Trek: Generations came along, Kirk would get another vest variant.
The various jackets and vests meshed nicely with the original Monster Maroon design to give the TOS film series the most varied uniform selection of any Star Trek incarnation. The film Maroon styles emulated the real world where different uniforms are worn for different jobs and functions. The Maroons helped Star Trek grow up a bit.