by interwar time the chemical industry produces virtually any colour you can desire.
fashion only limits the choice.
concidering the above avoid any colour/hues like: fluorescent or vivid colours, not so much denim jeans at least in the continental europe. in more conservative societies no reds as well, since it was regarded as the colour of the sin. for VBCW civilians in the conflict they must use everydayclothing and not the ones used for official receptions etc. Crimson and wine red colours might also be used for grooms etc for the hotels etc.
So, your palette may include every shade of greens, blues, brown, gray and blacks.
in summer lighter shdes and pale colours. white shirts a must (?).
the great fashion of the time was the gray (light gray/gris souris) raincoat for women and black /dark blue beret.