Why do giant squid have blue blood?

 A few weeks ago I attended at cinema showing of Inside Nature's Giants: The Giant Squid. In the series a team of experts dissect and examine some of the World's largest animals.

The giant squid (ref)

The Giant Squid is a little understood member of the class Cephalopoda, the cephalopods, known as Architeuthis dex (among other names). They are truly amazing animals, growing up to 20 meters long without a bone in their body (only a beak formed of protein and chitin).

Among the mysteries which were discussed in the programme and the Q&A session with some of the cast afterwards was the question;

"Why do giant squid have blue blood?"

The Constant Gardener

The Constant Gardener is a film and book, by acclaimed author John le Carré. Le Carré is better known for his Cold War spy novels, including The Spy Who Came In From The Cold and Tinker Tailor Soldier Spy. The Constant Gardener departs from this background, it is set in modern-day Kenya, dealing with issues of corruption, international aid and corporate evil. Without spoiling the ending, le Carré has written a wonderfully evocative critique of the western medical activities in Africa.