I got this problem during our most recent hiking trip. It served as a fun distraction and a way to kill time during our downhill hike. I will post the solution in about a week's time. Please feel free to post yours in the comment. The riddle credit goes to Vallent Lee.
On an isolated island there are 50 people with blue eyes, 50 people with brown eyes, and an oracle with green eyes. Every day at noon, a ship comes to the island. Anyone who can correctly mention his or her eye color can board the ship and leave.
One day, the oracle says "there is at least one person with blue eyes."
Who leaves the island and when?