You see you have gosteks who are colored already so you just need in player options put all clothes colors on white! Then the gosteks will be in the colors they are made in. Gosteks which are in black and white are suposed to be for color changing.Field marshal warned at that when he released his mod:
"The Fallschirmjager-Ardennes gostek, and the Metallkleidung are non grayscales. The rest however are all grayscales.
A little explination on the difference between grayscale and non grayscale, Grayscale simply means the gostek was designed to be able to be used with any color. Non grayscale means the gostek looks best in all white."
I think this isn't a bug