The Institute as a whole has a very clean and sterile (almost medical) aesthetic made up of smooth and elegant curves colored in a cold white, emphasizing both their advancement and detachment from the Commonwealth's horrors. Black is also sometimes associated with rebirth, and the East Coast Brotherhood has been reborn as a mighty Rising Empire in the decade since 3. Furthermore, while the Brotherhood are not precisely evil in this game, they're significantly Darker and Edgier than their counterparts in Fallout 3, and so a shift to a darker grey (almost black) can be seen as reflective of this increasing cynicism and darker turn.

Grey also evokes the image of plate armor and medieval knights, befitting the Brotherhood's Feudal Future aesthetic. Grey is also used for mourning (the Lyons family were wiped out in the decade since 3 and the Brotherhood has lost numerous soldiers to the Wasteland) and depression (as evidenced through the Brotherhood's increasingly cold and dour demeanor as they try to act like professional soldiers). Virtually all of the Brotherhood's technology has a clear grey color scheme thanks to their predominantly Diesel Punk aesthetic through their widespread usage of advanced Pre-War tech.

The East Coast Brotherhood of Steel - Grey/Black.

Even the fact that blue is symbolic of masculinity can be seen reflected in how the only active member of the Minutemen at the game's start is the male Preston Garvey. Blue also symbolizes serenity (the Minutemen are Reasonable Authority Figures to the settlements under their protection) and melancholia (the Minutemen suffered through a hideous Trauma Conga Line up to the present that left them shattered and relying on the Sole Survivor to help them rebuild). Blue is the most common favorite color, and the Minutemen are literally built up out of the Commonwealth's average settlers banding together for the common good. It also calls back to the Minutmen being (metaphorically) descended from the Pre-War United States in the use of blue from the American flag (along with a similar placement of stars). The Minutemen are the closest to a unambiguously 'good' faction in the whole game and so Blue Is Heroic is in full effect for them.

Color Motif: Each of the Commonwealth's primary factions have one or two colors be the most predominant in both their headquarters and equipment, usually being prominently featured on their flag (with the exception of the Brotherhood, whose flag is recolored orange in this game) and being heavily associated with their mood and aesthetic.

Gangs in fallout 4