Very few Irish families have their own tartan, and even the Irish county tartans are a recent innovation. For most of the 20th century the Irish wore solid-colored kilts when they wore kilts at all. Green, saffron, even blue kilts were worn. The House of Edgar introduced a line of Irish county tartans in the mid-1990s. The tartan for County Sligo, where the name Killoran apparently comes from, can be found here. To muddy the waters, Viking Technology Ltd. introduced an Irish "County Crest Range" of tartans, based on the heraldic arms of each county, in the first decade of this millennium. Their County Sligo tartan can be found here. Personally, I much prefer the House of Edgar designs. Keep in mind that in Ireland few people are likely to recognize any of these "Irish" tartans, let alone wear them. Also, I don't know anything about the history of your friend's family. I'm only suggesting a County Sligo tartan based on the supposed origin of the Killoran surname.