What chemical element gives the blood of a lobster and octopus a bluish tint?

Lobsters,octopus, snails, spiders and other creepy-crawlies have blood that uses copper for oxygen transport. This is called Hemocyanin. Oxygenation causes a color change between the colorless Cu deoxygenated form and the blue Cu oxygenated form. Vertebrates like humans , have iron based blood.