It is a much overlooked fact that all Celts have tartans, not just the Scotts. For example the national tartan of Kernow (Cornwall) is as follows:

White on Black for St. Piran’s Banner (The Patron Saint of Cornwall),

Black and Gold were the colours of the ancient Cornish kings,

Red is for the beak and legs of the Chough, the Cornish National bird,

Blue is for the sea surrounding Cornwall.