I fish from 10pm-12am about 4 nights a week, doing well on trout in the spring and fall, and I've been slamming smallies and an occcasional carp all summer. Some rules of thumb for me:
1.If there's no light anywhere (street lights, path lights, etc) go with black.
2.You're near a bridge or anything where some light hits the water, go with brighter colors. The original reason for black is so the fish can see the sillohuette against the night sky. If you're casting into some areas with light, fish will be hanging in the shadows and will see your offering drop into the light from a side view, and bright color helps when this happens. For me, I usually stick with white or chartreuse.
3.Subsurface - go big with the hackle as others have mentioned on streamers, also don't overlook a big meaty worm pattern. (look up Feathercraft's bugskin wiggler and oversize them)
4.Topwater - make lots of noise, make sure the fly plops down really hard on the water so the fish take notice. Keep the colors dark. Try adding some GID material as an indicator if you need it. Any combo of foam, hair, and rubber legs work. Try AZ mini hoppers or Hopper Juans in sizes 4-6.
5.Don't be afraid to fish close to shore. Browns especially are predators at night and might not be in that deep hole in the middle of the stream where you see them during the day. Strip up and down the banks and you'll have more luck.