Very interesting and thanks for the educational tip IluvVegas.
Also to add to that, from Wikipedia, "the Shamrock is a symbol of Ireland, and it is a three-leafed old white clover," not the green we thought it should be.
But, as IluvVegas mentions, it was changed to green by the Irish soldiers to gain attention from their government.
I'd say the Irish soldiers must have made a huge impact, since today we all think "green" is the color of the Irish and the Shamrock.