CHICAGO--(BUSINESS WIRE)--In response to the overwhelming outpour of Groupon’s signature green-themed celebrations the past few days, Groupon has issued a formal announcement of appreciation to the city of Chicago. Beginning on Saturday and through today, Chicagoans painted the entire city Groupon Green -- from attire and beverages to turning the Chicago River into an emerald cascade and TWO parades. “We are both honored and humbled that Chicago, the city we call home, has come together and pre