March 15, 2025- Chicago will dye the river bright green.

Originally, 100 pounds of a fluorescein dye, typically used to trace water currents, was used to create a vibrant green hue.

Today, the dye used is an eco-friendly vegetable-based dye, ensuring minimal impact on the river’s ecosystem. Additionally, the dye is now applied by specialized boats equipped with sprayers, ensuring a more even and vibrant coloration of the water.