Green
White and gold are also prominent.
Actually Blue was the original color until the clover was brought into it for the Father, Son, and the Holy Ghost....
Saint Patrick's ministry was in Ireland, and Ireland is known for its green landscape. Green is the color of Ireland (often called "The Emerald Isle"), the color of shamrocks, the official "Irish" color, as it were.
Saint Patrick's day begin in Ireland in the 9th and 10th centuries. It is celebrated around the world on March 17th.
Chicago.
purple
green (by the way it's favorite)
A shamrock.
Green is the primary color of St. Patrick's day.
Blue is the offical color of st patricks day.
Forty gallons of green vegetable dye are used to color the Chicago river for the St. Patrick's day celebration.