Q: So I know they always dye the Chicago River green on St. patrick's day, but how long does it take for the water to return to its normal colour?
A: Well they colored it Saturday at 10:45 am and by the time I was walking to work downtown Monday morning it was almost back to it's normal color. It's a non-toxic dye so it doesn't last too long and shouldn't harm the fish in the river. So, total it was about 2 days. The normal color is a dark muddy green, so it just gets darker again.