Heh. A website called House of Tartan has an automatic tartan generator: Just enter your favorite colors, pick the order and density of each thread count, and voila -- your own personal clan cloth. That one above? I generated it using the traditional heraldic colors of the House of Collision Detection: Dark blue, light blue, white and grey. Even cooler, House of Tartan actually has an option that lets you order bolts of cloth of your custom tartan, so I could make my own kilt!

As the site's history FAQ notes:

References to tartans occur in various historic documents, paintings and illustrations. A charter granted to Hector MacLean of Duart in 1587 for lands in Islay details a feu duty payable in the form of 60 ells cloth of white, black and green colours (the colours of Hunting MacLean of Duart tartan), and an eyewitness account of the Battle of Killecrankie in 1689 describes "McDonells men in their triple stripe". It is reasonable to assume that any tight knit community would wear the cloth produced by the local weaver in quantities that would limit the variety of patterns, and that when they went to war, many would be dressed in the same material.

I envision an enormous army of robots, all wearing my tartan as they fight bravely in the great squid uprising.

(Thanks to Simon Munro for this one!)