I've seen every color of light on piers. Mostly in Texas, I see lots of bright green floodlights, pointed downward, to attract fish. There are lots of underwater green lights set just off of piers as well, for attracting fish.

I suppose that if a pier is long enough to possibly conflict with vessel traffic, or if people go out on it at night, it ought to have some sort of lighting for safety reasons, along with a boarding ladder in case someone falls off, or for swimmer's convenience.