A Return of a Rainbow?

The taverns are full with Fey music for the festivities brought to the town.  Porters that have brought from the main land on the last ship are being served with some fresh corned beef cabbage, the aroma of meat fills the aid with. You notice a group of people are gathering at one of the windows looking out to port. You head their way and the group sees a beautiful rainbow in the distance heading out to sea…. the more you look at you begin to notice that it ends somewhere beyond the waters and you believe its leading to a strange island off the coast…… does this rainbow mean good fortunes for those that decide to venture there or could it mean something horrible could happen to those that are curious….only one way to find out….