You can decide and use the background of the whole crew: are they individuals gathering for a certain purpose, a gang or an official constituted team?
For example, I used to paint 3 of mine in the military scheme of the Firefly tv serie, red, brown and grey. And for the others, there is no uniform at all! (In this serie, some came from military and hired the others).
Using one specific color to identify your crew but in different clothes of the minis is also a good idea.
But what is really fun (for me) is first to imagine a little background for each mini and then to paint it: a scientist will have some white in his clothes, a soldier some green, etc...
But why not green and purple stripes? (I'm just thinking of it

). If you like vibrant colors, have a look at the Numenera rpg; if not, TV series and movies give you sober colors. Don't curb your imagination!
