Everything about Trench's outfit should be concealing and hint at her baggage. She refuses to open up, and the warfare-esque outfit should show how she views the world as scary and toxic. The basis of her clothes will be gray, as she is still a person, but all the hazmat/war accessories will be black to show that the dangers of the world deeply affect her. Especially with the pouch across her chest, it shows how she holds her baggage literally close to her heart.