By the way, great article and well researched.
I have a book intitled "The Irish Regiments" 1683-1999, in which an article concerning the dress of the Royal Inniskilling Fusiliers Pipers, the article would seem to suggest that the Inniskillings were the first to adopt a Kilt of non tartan type or Saffron on or around 7 July 1910. I would assume from the article that prior to this occassion that tartan kilts were worn...!