They didn't
edit:
there are a form powrie/dwarf/gremlin/goblin named red caps whose hats were stained with the blood of their victims.
In Gaelic tradition, leprechauns were said to wear red jackets.
Irish leprechauns are different from the Welsh versions of knocker, knacker, or bwca by the way they dress. Irish leprechauns of folklore typically wear a green or red coat. The Welsh leprechaun, or knocker, wear versions of miner's clothing.
If they wear a hat it will be
in his head
It is generally believed that leprechauns wearing green (as well as sitting on toadstools and having red beards) is borrowed from European folklore. The green uniform is considered to be a 20th century idea. The earliest accounts of leprechauns in Ireland depict them wearing red (and gold). They are often described as old, wrinkled men.
They wear green to hide better in keeping you from their gold.
There are only Leprechauns in Ireland and green is the National colour of Ireland.
They start screaming at you in Irish and their face turns red.
Tradition says leprechauns can't see green. So you pinch someone to warn them leprechauns can see them. You pinch them for their own safty.
Lspeedballs wear green because that is the irsh color for leprechauns. I know because I am one!
leprechauns are not used to symbolize the irish. the harp and the shamrock are by far the most wildly used images throughtout the world
In Celtic folktales, leprechauns were cranky souls, responsible for mending the shoes of the other fairies. Leprechauns were known for their trickery, which they often used to protect their much-fabled treasure.