Q: Why Do they wear green things when st particks main colour was blue?
A: You are correct that Blue was the color of ancient Ireland and St Patrick. The Green that we now know today is to symbolize the clover leaf that St Patrick used to describe the Holy Trinity of the Father, the Son, & the Holy Spirit. Green then began as an identifier with the Roman Catholic Church, then to Irish Nationalism (regardless of denominations) Especially under British rule. Today Green is so known world wide as the Irish color that most have forgotten about Blue.