UNSC Navy working uniform
From Halopedia, the Halo wiki
Working Uniforms are part of a uniform (much like fatigues) worn by military personnel in Non-Combat situations, such as the crew-members aboard the UNSC Pillar of Autumn[1] and UNSC In Amber Clad. They provide little to no protection, only offering a covering specifically for their jobs and tasks at hand, such as Engineering and Tech support on ships or ground-side.
Purpose
These uniforms offer only little protection and are not meant for combat personnel. Though they do come in a variety of colors such as blue, red, orange, purple, and yellow, as seen being worn by the crew in the "PoA". Such colors differs for what job they do, though they are not known for sure, personnel wearing orange, blue, and red can be seen operating computers on the bridge, Cryo bays, and anywhere else.
Behind the Scenes
In-game
As seen in the level Pillar of Autumn, crew-members had the ability to arm themselves, possibly being the ships "Security Force" when the Combat Personnel aren't present. Though, for those who fought, a few shots from a plasma bolt can bring down a crewman, seeing as the Uniform they wore weren't effective against Covenant plasma weapons.
Gallery
Working Uniforms or "Techie Uniforms" issued to Non-Combat Personnel.
The Naval Uniforms seen aboard the UNSC Pillar of Autumn.
