No, I think that you are right, Scrapheap. I think that the brown-eyed people leave too, but I think they leave 100 days after all the blue-eyed people leave, so on day 200. They figure it out the same way the blue-eyed people figured it out. Each of them sees 99 pairs of brown eyes and after 99 days of nobody else getting on the ferry, they figure out their own eye color has to be brown too, because if their own eyes were purple, then someone else with brown eyes would have seen this and left on day 99.