I think green, or more generally "earth tones" would be significant in space lore for life-symbolism, as might blue, if you assume 'green plants, blue water' to be dominant (which given that's it's space, is not guaranteed to be universal).

Possibly fire (red/orange) for the bad guys. Fire on a ship is especially bad news. Or since you imply they're unhinged, maybe go for ostentatious chaos in their manner of dress.