The river is traditionally dyed green for St. Patrick's Day.
If the Cubs win the World Series, the Chicago River will turn blue.
According to Michael Sneed of the Chicago Tribune, the city will dye the river Cubs blue if their beloved ballclub on the north side of town is able to down the Indians in the Fall Classic. The river is traditionally dyed green for St. Patrick's Day.
The Cubs trail the Indians 2–1 in the series with Game 4 on Saturday night at Wrigley Field. After Sunday’s Game 5, the series will head back to Cleveland. The franchise is trying for its first champinhship since 1908.
– Kenny Ducey