Well, in Ireland, where St. Patrick was a missionary, the national color was supposedly green, and the clover was probably first found there, which is of course, green.

Color green has come to be associated with St. Patrick’s Day over the last many centuries. Green themed parties are organized on this day where the food, the drinks as well as the decorations and clothing are green in color.

Green

Green is the primary color of St. Patrick's day.

Green is the color of the day!